How to convert any decimal number in form of $sqrt a+sqrt b$?












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Is there any method to directly convert any decimal number in form of $sqrt a+sqrt b$, given a and b are integers? Like $4.88=sqrt5+sqrt7$ (approximately)










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    $4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
    $endgroup$
    – Deepak
    Dec 2 '18 at 3:16












  • $begingroup$
    @martha Do you mean to convert any rational number?
    $endgroup$
    – Toby Mak
    Dec 2 '18 at 3:41






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    If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
    $endgroup$
    – Gerry Myerson
    Dec 2 '18 at 3:48
















0












$begingroup$


Is there any method to directly convert any decimal number in form of $sqrt a+sqrt b$, given a and b are integers? Like $4.88=sqrt5+sqrt7$ (approximately)










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    $4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
    $endgroup$
    – Deepak
    Dec 2 '18 at 3:16












  • $begingroup$
    @martha Do you mean to convert any rational number?
    $endgroup$
    – Toby Mak
    Dec 2 '18 at 3:41






  • 2




    $begingroup$
    If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
    $endgroup$
    – Gerry Myerson
    Dec 2 '18 at 3:48














0












0








0





$begingroup$


Is there any method to directly convert any decimal number in form of $sqrt a+sqrt b$, given a and b are integers? Like $4.88=sqrt5+sqrt7$ (approximately)










share|cite|improve this question











$endgroup$




Is there any method to directly convert any decimal number in form of $sqrt a+sqrt b$, given a and b are integers? Like $4.88=sqrt5+sqrt7$ (approximately)







irrational-numbers






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share|cite|improve this question













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edited Dec 2 '18 at 7:21









Tianlalu

3,08121038




3,08121038










asked Dec 2 '18 at 3:14









marthamartha

71




71








  • 1




    $begingroup$
    $4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
    $endgroup$
    – Deepak
    Dec 2 '18 at 3:16












  • $begingroup$
    @martha Do you mean to convert any rational number?
    $endgroup$
    – Toby Mak
    Dec 2 '18 at 3:41






  • 2




    $begingroup$
    If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
    $endgroup$
    – Gerry Myerson
    Dec 2 '18 at 3:48














  • 1




    $begingroup$
    $4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
    $endgroup$
    – Deepak
    Dec 2 '18 at 3:16












  • $begingroup$
    @martha Do you mean to convert any rational number?
    $endgroup$
    – Toby Mak
    Dec 2 '18 at 3:41






  • 2




    $begingroup$
    If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
    $endgroup$
    – Gerry Myerson
    Dec 2 '18 at 3:48








1




1




$begingroup$
$4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
$endgroup$
– Deepak
Dec 2 '18 at 3:16






$begingroup$
$4.88 neq sqrt 5 + sqrt 7$ LHS is rational, RHS is irrational. If you'd written $4.88 approx sqrt 5 + sqrt 7$ that would be acceptable.
$endgroup$
– Deepak
Dec 2 '18 at 3:16














$begingroup$
@martha Do you mean to convert any rational number?
$endgroup$
– Toby Mak
Dec 2 '18 at 3:41




$begingroup$
@martha Do you mean to convert any rational number?
$endgroup$
– Toby Mak
Dec 2 '18 at 3:41




2




2




$begingroup$
If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
$endgroup$
– Gerry Myerson
Dec 2 '18 at 3:48




$begingroup$
If $r=sqrt a+sqrt b$, then $rgesqrt a$, so $ale r^2$, and similarly $ble r^2$. So if worst comes to worst you can just check every pair $(a,b)$ up to $r^2$ to see which one comes closest. Not quite as bad as it sounds, as for each value of $a$ that you try, you can compute $(r-sqrt a)^2$ to see what value of $b$ to try.
$endgroup$
– Gerry Myerson
Dec 2 '18 at 3:48










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