Method to factor an expression












1












$begingroup$


As the title says, i want to factorize an expression, but i don't have any clue how to proceed.



Here is the expression :



$2x² -7x +3$



And here is the factorized form :



$(x-3)(2x - 1)$



My question is, which method or rule to use to go from first to second ?



please note that I am a beginner, and the only question that i found which is closer to mine is this post.



Thank you for your help !










share|cite|improve this question









$endgroup$

















    1












    $begingroup$


    As the title says, i want to factorize an expression, but i don't have any clue how to proceed.



    Here is the expression :



    $2x² -7x +3$



    And here is the factorized form :



    $(x-3)(2x - 1)$



    My question is, which method or rule to use to go from first to second ?



    please note that I am a beginner, and the only question that i found which is closer to mine is this post.



    Thank you for your help !










    share|cite|improve this question









    $endgroup$















      1












      1








      1


      1



      $begingroup$


      As the title says, i want to factorize an expression, but i don't have any clue how to proceed.



      Here is the expression :



      $2x² -7x +3$



      And here is the factorized form :



      $(x-3)(2x - 1)$



      My question is, which method or rule to use to go from first to second ?



      please note that I am a beginner, and the only question that i found which is closer to mine is this post.



      Thank you for your help !










      share|cite|improve this question









      $endgroup$




      As the title says, i want to factorize an expression, but i don't have any clue how to proceed.



      Here is the expression :



      $2x² -7x +3$



      And here is the factorized form :



      $(x-3)(2x - 1)$



      My question is, which method or rule to use to go from first to second ?



      please note that I am a beginner, and the only question that i found which is closer to mine is this post.



      Thank you for your help !







      factoring






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Dec 18 '18 at 9:18









      ganzo dbganzo db

      155




      155






















          4 Answers
          4






          active

          oldest

          votes


















          3












          $begingroup$

          Rewrite the expression into the form:



          $2x^2-6x-x+3$ ,



          then group the first two terms together and the last two terms together:



          $(2x^2-6x)-(x-3)=2x(x-3)-(x-3)$ ,



          next extract the common factor:



          $(x-3)(2x-1)$ ,



          and you are done.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I like the simplicity of your method, thank's :)
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:41










          • $begingroup$
            @ganzodb You are welcome
            $endgroup$
            – Matko
            Dec 18 '18 at 18:24



















          2












          $begingroup$

          If it concerns quadratic polynomial $ax^2+bx+c$ then start with calculating discriminant: $$D:=b^2-4ac$$



          If $D$ is negative then give up (unless you are familiar with complex numbers already).



          If $D$ is nonnegative then: $$ax^2+bx+c=a(x-x_1)(x-x_2)$$ where $x_1=frac{-b+sqrt D}{2a}$ and $x_2=frac{-b-sqrt D}{2a}$.



          Especially if $D$ is a perfect square (as in your case, where $D=25$) then there is reason to cheer.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            As you supposed, i'm not good with complex numbers :) !
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:54



















          2












          $begingroup$

          It relies on the following property of quadratic polynomials:




          If the quadratic polynomial $;ax^2+bx+c;(ane 0)$ has roots $xi_0$ and $xi_1$ (real or complex, distinct ot not), it can factored as
          $$ax^2+bx+c=a(x-xi_0)(x-xi_1).$$




          This property is a consequence of a more general property of polynomials (of any degree) and the ring of polynomials over a field being a euclidean domain:




          If a polynomial $p(x)$ has root $xi$, it is divisible by $x-xi$.




          In the present case, the discriminat of $2x² -7x +3$ is $;Delta=49-4cdot 2cdot 3=25$, so its roots are $;frac{7pm 5}4==bigl{3,frac 12bigr}$, and the factorisation is
          $$2(x-3)Bigl(x-frac12Bigr)=(x-3)(2x-1).$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            i wish i could understand the last one ( frac{7pm 5}4 ).
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:57








          • 2




            $begingroup$
            @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
            $endgroup$
            – Bernard
            Dec 18 '18 at 18:22



















          2












          $begingroup$

          In general ,if $x_1$ and $x_2$ are roots of $$underbrace{a}_{neq 0}x^2+bx+c=0$$ then $$ax^2+bx+c=k(x-x_1)(x-x_2)=k[x^2-(x_1+x_2)x+x_1x_2]$$ comparing the coefficients, $$a=k,b=-k(x_1+x_2),c=kx_1x_2$$ Consequently $$text{sum of the roots}=-frac{b}{a};;&;;text{product of the roots}=frac{c}{a}$$





          So your case, $x_1+x_2= frac{7}{2}$ and $x_1x_2=frac{3}{2}$



          Now solve these to get $x_1$ and $x_2$ to finish your conclusion





          To find $x_1$ and $x_2$, $$2x^2-7x+3=0$$ implies $$x^2-frac{7}{2}x+frac{3}{2}=0$$ which means $$x^2-2left(frac{7}{4}right)x=-frac{3}{2}$$ which is same as $$x^2-2left(frac{7}{4}right)x+frac{49}{16}=-frac{3}{2}+frac{49}{16}=frac{25}{16}$$ so $$left(x-frac{7}{4}right)^2=frac{25}{16}$$ and so $$x-frac{7}{4}=pm sqrt{frac{25}{16}}=pm frac{5}{4}$$ so $$x=frac{7}{4} pm frac{5}{4}=frac{7pm 5}{4}$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:53











          Your Answer





          StackExchange.ifUsing("editor", function () {
          return StackExchange.using("mathjaxEditing", function () {
          StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
          StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
          });
          });
          }, "mathjax-editing");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "69"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          noCode: true, onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3044937%2fmethod-to-factor-an-expression%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          4 Answers
          4






          active

          oldest

          votes








          4 Answers
          4






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          3












          $begingroup$

          Rewrite the expression into the form:



          $2x^2-6x-x+3$ ,



          then group the first two terms together and the last two terms together:



          $(2x^2-6x)-(x-3)=2x(x-3)-(x-3)$ ,



          next extract the common factor:



          $(x-3)(2x-1)$ ,



          and you are done.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I like the simplicity of your method, thank's :)
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:41










          • $begingroup$
            @ganzodb You are welcome
            $endgroup$
            – Matko
            Dec 18 '18 at 18:24
















          3












          $begingroup$

          Rewrite the expression into the form:



          $2x^2-6x-x+3$ ,



          then group the first two terms together and the last two terms together:



          $(2x^2-6x)-(x-3)=2x(x-3)-(x-3)$ ,



          next extract the common factor:



          $(x-3)(2x-1)$ ,



          and you are done.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            I like the simplicity of your method, thank's :)
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:41










          • $begingroup$
            @ganzodb You are welcome
            $endgroup$
            – Matko
            Dec 18 '18 at 18:24














          3












          3








          3





          $begingroup$

          Rewrite the expression into the form:



          $2x^2-6x-x+3$ ,



          then group the first two terms together and the last two terms together:



          $(2x^2-6x)-(x-3)=2x(x-3)-(x-3)$ ,



          next extract the common factor:



          $(x-3)(2x-1)$ ,



          and you are done.






          share|cite|improve this answer











          $endgroup$



          Rewrite the expression into the form:



          $2x^2-6x-x+3$ ,



          then group the first two terms together and the last two terms together:



          $(2x^2-6x)-(x-3)=2x(x-3)-(x-3)$ ,



          next extract the common factor:



          $(x-3)(2x-1)$ ,



          and you are done.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 18 '18 at 10:11

























          answered Dec 18 '18 at 10:05









          MatkoMatko

          864




          864












          • $begingroup$
            I like the simplicity of your method, thank's :)
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:41










          • $begingroup$
            @ganzodb You are welcome
            $endgroup$
            – Matko
            Dec 18 '18 at 18:24


















          • $begingroup$
            I like the simplicity of your method, thank's :)
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:41










          • $begingroup$
            @ganzodb You are welcome
            $endgroup$
            – Matko
            Dec 18 '18 at 18:24
















          $begingroup$
          I like the simplicity of your method, thank's :)
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:41




          $begingroup$
          I like the simplicity of your method, thank's :)
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:41












          $begingroup$
          @ganzodb You are welcome
          $endgroup$
          – Matko
          Dec 18 '18 at 18:24




          $begingroup$
          @ganzodb You are welcome
          $endgroup$
          – Matko
          Dec 18 '18 at 18:24











          2












          $begingroup$

          If it concerns quadratic polynomial $ax^2+bx+c$ then start with calculating discriminant: $$D:=b^2-4ac$$



          If $D$ is negative then give up (unless you are familiar with complex numbers already).



          If $D$ is nonnegative then: $$ax^2+bx+c=a(x-x_1)(x-x_2)$$ where $x_1=frac{-b+sqrt D}{2a}$ and $x_2=frac{-b-sqrt D}{2a}$.



          Especially if $D$ is a perfect square (as in your case, where $D=25$) then there is reason to cheer.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            As you supposed, i'm not good with complex numbers :) !
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:54
















          2












          $begingroup$

          If it concerns quadratic polynomial $ax^2+bx+c$ then start with calculating discriminant: $$D:=b^2-4ac$$



          If $D$ is negative then give up (unless you are familiar with complex numbers already).



          If $D$ is nonnegative then: $$ax^2+bx+c=a(x-x_1)(x-x_2)$$ where $x_1=frac{-b+sqrt D}{2a}$ and $x_2=frac{-b-sqrt D}{2a}$.



          Especially if $D$ is a perfect square (as in your case, where $D=25$) then there is reason to cheer.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            As you supposed, i'm not good with complex numbers :) !
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:54














          2












          2








          2





          $begingroup$

          If it concerns quadratic polynomial $ax^2+bx+c$ then start with calculating discriminant: $$D:=b^2-4ac$$



          If $D$ is negative then give up (unless you are familiar with complex numbers already).



          If $D$ is nonnegative then: $$ax^2+bx+c=a(x-x_1)(x-x_2)$$ where $x_1=frac{-b+sqrt D}{2a}$ and $x_2=frac{-b-sqrt D}{2a}$.



          Especially if $D$ is a perfect square (as in your case, where $D=25$) then there is reason to cheer.






          share|cite|improve this answer









          $endgroup$



          If it concerns quadratic polynomial $ax^2+bx+c$ then start with calculating discriminant: $$D:=b^2-4ac$$



          If $D$ is negative then give up (unless you are familiar with complex numbers already).



          If $D$ is nonnegative then: $$ax^2+bx+c=a(x-x_1)(x-x_2)$$ where $x_1=frac{-b+sqrt D}{2a}$ and $x_2=frac{-b-sqrt D}{2a}$.



          Especially if $D$ is a perfect square (as in your case, where $D=25$) then there is reason to cheer.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 18 '18 at 9:39









          drhabdrhab

          101k545136




          101k545136












          • $begingroup$
            As you supposed, i'm not good with complex numbers :) !
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:54


















          • $begingroup$
            As you supposed, i'm not good with complex numbers :) !
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:54
















          $begingroup$
          As you supposed, i'm not good with complex numbers :) !
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:54




          $begingroup$
          As you supposed, i'm not good with complex numbers :) !
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:54











          2












          $begingroup$

          It relies on the following property of quadratic polynomials:




          If the quadratic polynomial $;ax^2+bx+c;(ane 0)$ has roots $xi_0$ and $xi_1$ (real or complex, distinct ot not), it can factored as
          $$ax^2+bx+c=a(x-xi_0)(x-xi_1).$$




          This property is a consequence of a more general property of polynomials (of any degree) and the ring of polynomials over a field being a euclidean domain:




          If a polynomial $p(x)$ has root $xi$, it is divisible by $x-xi$.




          In the present case, the discriminat of $2x² -7x +3$ is $;Delta=49-4cdot 2cdot 3=25$, so its roots are $;frac{7pm 5}4==bigl{3,frac 12bigr}$, and the factorisation is
          $$2(x-3)Bigl(x-frac12Bigr)=(x-3)(2x-1).$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            i wish i could understand the last one ( frac{7pm 5}4 ).
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:57








          • 2




            $begingroup$
            @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
            $endgroup$
            – Bernard
            Dec 18 '18 at 18:22
















          2












          $begingroup$

          It relies on the following property of quadratic polynomials:




          If the quadratic polynomial $;ax^2+bx+c;(ane 0)$ has roots $xi_0$ and $xi_1$ (real or complex, distinct ot not), it can factored as
          $$ax^2+bx+c=a(x-xi_0)(x-xi_1).$$




          This property is a consequence of a more general property of polynomials (of any degree) and the ring of polynomials over a field being a euclidean domain:




          If a polynomial $p(x)$ has root $xi$, it is divisible by $x-xi$.




          In the present case, the discriminat of $2x² -7x +3$ is $;Delta=49-4cdot 2cdot 3=25$, so its roots are $;frac{7pm 5}4==bigl{3,frac 12bigr}$, and the factorisation is
          $$2(x-3)Bigl(x-frac12Bigr)=(x-3)(2x-1).$$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            i wish i could understand the last one ( frac{7pm 5}4 ).
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:57








          • 2




            $begingroup$
            @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
            $endgroup$
            – Bernard
            Dec 18 '18 at 18:22














          2












          2








          2





          $begingroup$

          It relies on the following property of quadratic polynomials:




          If the quadratic polynomial $;ax^2+bx+c;(ane 0)$ has roots $xi_0$ and $xi_1$ (real or complex, distinct ot not), it can factored as
          $$ax^2+bx+c=a(x-xi_0)(x-xi_1).$$




          This property is a consequence of a more general property of polynomials (of any degree) and the ring of polynomials over a field being a euclidean domain:




          If a polynomial $p(x)$ has root $xi$, it is divisible by $x-xi$.




          In the present case, the discriminat of $2x² -7x +3$ is $;Delta=49-4cdot 2cdot 3=25$, so its roots are $;frac{7pm 5}4==bigl{3,frac 12bigr}$, and the factorisation is
          $$2(x-3)Bigl(x-frac12Bigr)=(x-3)(2x-1).$$






          share|cite|improve this answer









          $endgroup$



          It relies on the following property of quadratic polynomials:




          If the quadratic polynomial $;ax^2+bx+c;(ane 0)$ has roots $xi_0$ and $xi_1$ (real or complex, distinct ot not), it can factored as
          $$ax^2+bx+c=a(x-xi_0)(x-xi_1).$$




          This property is a consequence of a more general property of polynomials (of any degree) and the ring of polynomials over a field being a euclidean domain:




          If a polynomial $p(x)$ has root $xi$, it is divisible by $x-xi$.




          In the present case, the discriminat of $2x² -7x +3$ is $;Delta=49-4cdot 2cdot 3=25$, so its roots are $;frac{7pm 5}4==bigl{3,frac 12bigr}$, and the factorisation is
          $$2(x-3)Bigl(x-frac12Bigr)=(x-3)(2x-1).$$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 18 '18 at 9:40









          BernardBernard

          121k740116




          121k740116












          • $begingroup$
            i wish i could understand the last one ( frac{7pm 5}4 ).
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:57








          • 2




            $begingroup$
            @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
            $endgroup$
            – Bernard
            Dec 18 '18 at 18:22


















          • $begingroup$
            i wish i could understand the last one ( frac{7pm 5}4 ).
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:57








          • 2




            $begingroup$
            @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
            $endgroup$
            – Bernard
            Dec 18 '18 at 18:22
















          $begingroup$
          i wish i could understand the last one ( frac{7pm 5}4 ).
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:57






          $begingroup$
          i wish i could understand the last one ( frac{7pm 5}4 ).
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:57






          2




          2




          $begingroup$
          @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
          $endgroup$
          – Bernard
          Dec 18 '18 at 18:22




          $begingroup$
          @ganzodb: It's just the formula $frac{-bpmsqrtDelta}{2a}.$.
          $endgroup$
          – Bernard
          Dec 18 '18 at 18:22











          2












          $begingroup$

          In general ,if $x_1$ and $x_2$ are roots of $$underbrace{a}_{neq 0}x^2+bx+c=0$$ then $$ax^2+bx+c=k(x-x_1)(x-x_2)=k[x^2-(x_1+x_2)x+x_1x_2]$$ comparing the coefficients, $$a=k,b=-k(x_1+x_2),c=kx_1x_2$$ Consequently $$text{sum of the roots}=-frac{b}{a};;&;;text{product of the roots}=frac{c}{a}$$





          So your case, $x_1+x_2= frac{7}{2}$ and $x_1x_2=frac{3}{2}$



          Now solve these to get $x_1$ and $x_2$ to finish your conclusion





          To find $x_1$ and $x_2$, $$2x^2-7x+3=0$$ implies $$x^2-frac{7}{2}x+frac{3}{2}=0$$ which means $$x^2-2left(frac{7}{4}right)x=-frac{3}{2}$$ which is same as $$x^2-2left(frac{7}{4}right)x+frac{49}{16}=-frac{3}{2}+frac{49}{16}=frac{25}{16}$$ so $$left(x-frac{7}{4}right)^2=frac{25}{16}$$ and so $$x-frac{7}{4}=pm sqrt{frac{25}{16}}=pm frac{5}{4}$$ so $$x=frac{7}{4} pm frac{5}{4}=frac{7pm 5}{4}$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:53
















          2












          $begingroup$

          In general ,if $x_1$ and $x_2$ are roots of $$underbrace{a}_{neq 0}x^2+bx+c=0$$ then $$ax^2+bx+c=k(x-x_1)(x-x_2)=k[x^2-(x_1+x_2)x+x_1x_2]$$ comparing the coefficients, $$a=k,b=-k(x_1+x_2),c=kx_1x_2$$ Consequently $$text{sum of the roots}=-frac{b}{a};;&;;text{product of the roots}=frac{c}{a}$$





          So your case, $x_1+x_2= frac{7}{2}$ and $x_1x_2=frac{3}{2}$



          Now solve these to get $x_1$ and $x_2$ to finish your conclusion





          To find $x_1$ and $x_2$, $$2x^2-7x+3=0$$ implies $$x^2-frac{7}{2}x+frac{3}{2}=0$$ which means $$x^2-2left(frac{7}{4}right)x=-frac{3}{2}$$ which is same as $$x^2-2left(frac{7}{4}right)x+frac{49}{16}=-frac{3}{2}+frac{49}{16}=frac{25}{16}$$ so $$left(x-frac{7}{4}right)^2=frac{25}{16}$$ and so $$x-frac{7}{4}=pm sqrt{frac{25}{16}}=pm frac{5}{4}$$ so $$x=frac{7}{4} pm frac{5}{4}=frac{7pm 5}{4}$$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:53














          2












          2








          2





          $begingroup$

          In general ,if $x_1$ and $x_2$ are roots of $$underbrace{a}_{neq 0}x^2+bx+c=0$$ then $$ax^2+bx+c=k(x-x_1)(x-x_2)=k[x^2-(x_1+x_2)x+x_1x_2]$$ comparing the coefficients, $$a=k,b=-k(x_1+x_2),c=kx_1x_2$$ Consequently $$text{sum of the roots}=-frac{b}{a};;&;;text{product of the roots}=frac{c}{a}$$





          So your case, $x_1+x_2= frac{7}{2}$ and $x_1x_2=frac{3}{2}$



          Now solve these to get $x_1$ and $x_2$ to finish your conclusion





          To find $x_1$ and $x_2$, $$2x^2-7x+3=0$$ implies $$x^2-frac{7}{2}x+frac{3}{2}=0$$ which means $$x^2-2left(frac{7}{4}right)x=-frac{3}{2}$$ which is same as $$x^2-2left(frac{7}{4}right)x+frac{49}{16}=-frac{3}{2}+frac{49}{16}=frac{25}{16}$$ so $$left(x-frac{7}{4}right)^2=frac{25}{16}$$ and so $$x-frac{7}{4}=pm sqrt{frac{25}{16}}=pm frac{5}{4}$$ so $$x=frac{7}{4} pm frac{5}{4}=frac{7pm 5}{4}$$






          share|cite|improve this answer











          $endgroup$



          In general ,if $x_1$ and $x_2$ are roots of $$underbrace{a}_{neq 0}x^2+bx+c=0$$ then $$ax^2+bx+c=k(x-x_1)(x-x_2)=k[x^2-(x_1+x_2)x+x_1x_2]$$ comparing the coefficients, $$a=k,b=-k(x_1+x_2),c=kx_1x_2$$ Consequently $$text{sum of the roots}=-frac{b}{a};;&;;text{product of the roots}=frac{c}{a}$$





          So your case, $x_1+x_2= frac{7}{2}$ and $x_1x_2=frac{3}{2}$



          Now solve these to get $x_1$ and $x_2$ to finish your conclusion





          To find $x_1$ and $x_2$, $$2x^2-7x+3=0$$ implies $$x^2-frac{7}{2}x+frac{3}{2}=0$$ which means $$x^2-2left(frac{7}{4}right)x=-frac{3}{2}$$ which is same as $$x^2-2left(frac{7}{4}right)x+frac{49}{16}=-frac{3}{2}+frac{49}{16}=frac{25}{16}$$ so $$left(x-frac{7}{4}right)^2=frac{25}{16}$$ and so $$x-frac{7}{4}=pm sqrt{frac{25}{16}}=pm frac{5}{4}$$ so $$x=frac{7}{4} pm frac{5}{4}=frac{7pm 5}{4}$$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Dec 18 '18 at 10:17

























          answered Dec 18 '18 at 10:04









          Chinnapparaj RChinnapparaj R

          5,4872928




          5,4872928












          • $begingroup$
            Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:53


















          • $begingroup$
            Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
            $endgroup$
            – ganzo db
            Dec 18 '18 at 16:53
















          $begingroup$
          Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:53




          $begingroup$
          Thank you for the time spent in the explanation, i'm still unfamiliar with some mathematical concepts.
          $endgroup$
          – ganzo db
          Dec 18 '18 at 16:53


















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Mathematics Stack Exchange!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          Use MathJax to format equations. MathJax reference.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3044937%2fmethod-to-factor-an-expression%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          Popular posts from this blog

          Ellipse (mathématiques)

          Quarter-circle Tiles

          Mont Emei