Can the sum, difference and product of 2 numbers be perfect squares? [closed]












2












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If we take 2 numbers $x$ and $y$ such that $x>y>0$ and , can $x + y$, $x - y$ and $xy$ all be perfect squares?










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$endgroup$



closed as off-topic by rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter Jan 7 at 16:54


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is off-topic as it appears to be a mathematics problem, as opposed to a mathematical puzzle. For more info, see "Are math-textbook-style problems on topic?" on meta." – rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter

If this question can be reworded to fit the rules in the help center, please edit the question.












  • 1




    $begingroup$
    Is this on topic? Feels like a math question
    $endgroup$
    – Dr Xorile
    Jan 7 at 15:05










  • $begingroup$
    No I made it myself but could not solve it.
    $endgroup$
    – Magic turtle
    Jan 7 at 15:06
















2












$begingroup$


If we take 2 numbers $x$ and $y$ such that $x>y>0$ and , can $x + y$, $x - y$ and $xy$ all be perfect squares?










share|improve this question











$endgroup$



closed as off-topic by rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter Jan 7 at 16:54


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is off-topic as it appears to be a mathematics problem, as opposed to a mathematical puzzle. For more info, see "Are math-textbook-style problems on topic?" on meta." – rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter

If this question can be reworded to fit the rules in the help center, please edit the question.












  • 1




    $begingroup$
    Is this on topic? Feels like a math question
    $endgroup$
    – Dr Xorile
    Jan 7 at 15:05










  • $begingroup$
    No I made it myself but could not solve it.
    $endgroup$
    – Magic turtle
    Jan 7 at 15:06














2












2








2


0



$begingroup$


If we take 2 numbers $x$ and $y$ such that $x>y>0$ and , can $x + y$, $x - y$ and $xy$ all be perfect squares?










share|improve this question











$endgroup$




If we take 2 numbers $x$ and $y$ such that $x>y>0$ and , can $x + y$, $x - y$ and $xy$ all be perfect squares?







mathematics number-theory algebra






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Jan 7 at 14:09







Magic turtle

















asked Jan 7 at 12:55









Magic turtleMagic turtle

566




566




closed as off-topic by rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter Jan 7 at 16:54


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is off-topic as it appears to be a mathematics problem, as opposed to a mathematical puzzle. For more info, see "Are math-textbook-style problems on topic?" on meta." – rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter

If this question can be reworded to fit the rules in the help center, please edit the question.







closed as off-topic by rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter Jan 7 at 16:54


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is off-topic as it appears to be a mathematics problem, as opposed to a mathematical puzzle. For more info, see "Are math-textbook-style problems on topic?" on meta." – rhsquared, Glorfindel, JonMark Perry, Excited Raichu, ABcDexter

If this question can be reworded to fit the rules in the help center, please edit the question.








  • 1




    $begingroup$
    Is this on topic? Feels like a math question
    $endgroup$
    – Dr Xorile
    Jan 7 at 15:05










  • $begingroup$
    No I made it myself but could not solve it.
    $endgroup$
    – Magic turtle
    Jan 7 at 15:06














  • 1




    $begingroup$
    Is this on topic? Feels like a math question
    $endgroup$
    – Dr Xorile
    Jan 7 at 15:05










  • $begingroup$
    No I made it myself but could not solve it.
    $endgroup$
    – Magic turtle
    Jan 7 at 15:06








1




1




$begingroup$
Is this on topic? Feels like a math question
$endgroup$
– Dr Xorile
Jan 7 at 15:05




$begingroup$
Is this on topic? Feels like a math question
$endgroup$
– Dr Xorile
Jan 7 at 15:05












$begingroup$
No I made it myself but could not solve it.
$endgroup$
– Magic turtle
Jan 7 at 15:06




$begingroup$
No I made it myself but could not solve it.
$endgroup$
– Magic turtle
Jan 7 at 15:06










2 Answers
2






active

oldest

votes


















4












$begingroup$

The answer is




that they cannot.




Suppose $x+y=a^2$ and $x-y=b^2$. Then




$x,y=frac{a^2pm b^2}2$ and therefore $4xy=a^4-b^4$. So if this too is a square we have $a^4-b^4=c^2$. Now see https://math.stackexchange.com/questions/153546/solving-x4-y4-z2 where it is shown that there are no solutions to this equation in nonzero integers.







share|improve this answer









$endgroup$













  • $begingroup$
    "if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
    $endgroup$
    – UKMonkey
    Jan 7 at 17:10












  • $begingroup$
    If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
    $endgroup$
    – Gareth McCaughan
    Jan 7 at 18:56



















2












$begingroup$

(Before the OP clarifying that 0 is disallowed)



Yes.




x = 4, y = 0; x+y = 4, x-y = 4, xy = 0. (x can be any perfect square, I just decided to use 4)







share|improve this answer











$endgroup$













  • $begingroup$
    Sorry my fault, I meant to include that y cannot = 0.
    $endgroup$
    – Magic turtle
    Jan 7 at 14:10










  • $begingroup$
    But can x be 0?
    $endgroup$
    – Ian MacDonald
    Jan 7 at 14:17










  • $begingroup$
    If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
    $endgroup$
    – Magic turtle
    Jan 7 at 14:30


















2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









4












$begingroup$

The answer is




that they cannot.




Suppose $x+y=a^2$ and $x-y=b^2$. Then




$x,y=frac{a^2pm b^2}2$ and therefore $4xy=a^4-b^4$. So if this too is a square we have $a^4-b^4=c^2$. Now see https://math.stackexchange.com/questions/153546/solving-x4-y4-z2 where it is shown that there are no solutions to this equation in nonzero integers.







share|improve this answer









$endgroup$













  • $begingroup$
    "if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
    $endgroup$
    – UKMonkey
    Jan 7 at 17:10












  • $begingroup$
    If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
    $endgroup$
    – Gareth McCaughan
    Jan 7 at 18:56
















4












$begingroup$

The answer is




that they cannot.




Suppose $x+y=a^2$ and $x-y=b^2$. Then




$x,y=frac{a^2pm b^2}2$ and therefore $4xy=a^4-b^4$. So if this too is a square we have $a^4-b^4=c^2$. Now see https://math.stackexchange.com/questions/153546/solving-x4-y4-z2 where it is shown that there are no solutions to this equation in nonzero integers.







share|improve this answer









$endgroup$













  • $begingroup$
    "if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
    $endgroup$
    – UKMonkey
    Jan 7 at 17:10












  • $begingroup$
    If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
    $endgroup$
    – Gareth McCaughan
    Jan 7 at 18:56














4












4








4





$begingroup$

The answer is




that they cannot.




Suppose $x+y=a^2$ and $x-y=b^2$. Then




$x,y=frac{a^2pm b^2}2$ and therefore $4xy=a^4-b^4$. So if this too is a square we have $a^4-b^4=c^2$. Now see https://math.stackexchange.com/questions/153546/solving-x4-y4-z2 where it is shown that there are no solutions to this equation in nonzero integers.







share|improve this answer









$endgroup$



The answer is




that they cannot.




Suppose $x+y=a^2$ and $x-y=b^2$. Then




$x,y=frac{a^2pm b^2}2$ and therefore $4xy=a^4-b^4$. So if this too is a square we have $a^4-b^4=c^2$. Now see https://math.stackexchange.com/questions/153546/solving-x4-y4-z2 where it is shown that there are no solutions to this equation in nonzero integers.








share|improve this answer












share|improve this answer



share|improve this answer










answered Jan 7 at 14:15









Gareth McCaughanGareth McCaughan

61.1k3152236




61.1k3152236












  • $begingroup$
    "if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
    $endgroup$
    – UKMonkey
    Jan 7 at 17:10












  • $begingroup$
    If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
    $endgroup$
    – Gareth McCaughan
    Jan 7 at 18:56


















  • $begingroup$
    "if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
    $endgroup$
    – UKMonkey
    Jan 7 at 17:10












  • $begingroup$
    If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
    $endgroup$
    – Gareth McCaughan
    Jan 7 at 18:56
















$begingroup$
"if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
$endgroup$
– UKMonkey
Jan 7 at 17:10






$begingroup$
"if this too is a square" we have (a^4 -b^4) / 4 = c^2 ... The fact that you binned y=0 means that the proof doesn't hold for this alternate equation
$endgroup$
– UKMonkey
Jan 7 at 17:10














$begingroup$
If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
$endgroup$
– Gareth McCaughan
Jan 7 at 18:56




$begingroup$
If 4xy is a square then xy is also a square. I'm not sure what you mean by "you binned y=0" but the question itself specifies that y>0.
$endgroup$
– Gareth McCaughan
Jan 7 at 18:56











2












$begingroup$

(Before the OP clarifying that 0 is disallowed)



Yes.




x = 4, y = 0; x+y = 4, x-y = 4, xy = 0. (x can be any perfect square, I just decided to use 4)







share|improve this answer











$endgroup$













  • $begingroup$
    Sorry my fault, I meant to include that y cannot = 0.
    $endgroup$
    – Magic turtle
    Jan 7 at 14:10










  • $begingroup$
    But can x be 0?
    $endgroup$
    – Ian MacDonald
    Jan 7 at 14:17










  • $begingroup$
    If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
    $endgroup$
    – Magic turtle
    Jan 7 at 14:30
















2












$begingroup$

(Before the OP clarifying that 0 is disallowed)



Yes.




x = 4, y = 0; x+y = 4, x-y = 4, xy = 0. (x can be any perfect square, I just decided to use 4)







share|improve this answer











$endgroup$













  • $begingroup$
    Sorry my fault, I meant to include that y cannot = 0.
    $endgroup$
    – Magic turtle
    Jan 7 at 14:10










  • $begingroup$
    But can x be 0?
    $endgroup$
    – Ian MacDonald
    Jan 7 at 14:17










  • $begingroup$
    If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
    $endgroup$
    – Magic turtle
    Jan 7 at 14:30














2












2








2





$begingroup$

(Before the OP clarifying that 0 is disallowed)



Yes.




x = 4, y = 0; x+y = 4, x-y = 4, xy = 0. (x can be any perfect square, I just decided to use 4)







share|improve this answer











$endgroup$



(Before the OP clarifying that 0 is disallowed)



Yes.




x = 4, y = 0; x+y = 4, x-y = 4, xy = 0. (x can be any perfect square, I just decided to use 4)








share|improve this answer














share|improve this answer



share|improve this answer








edited Jan 7 at 14:17

























answered Jan 7 at 12:56









Excited RaichuExcited Raichu

6,43521166




6,43521166












  • $begingroup$
    Sorry my fault, I meant to include that y cannot = 0.
    $endgroup$
    – Magic turtle
    Jan 7 at 14:10










  • $begingroup$
    But can x be 0?
    $endgroup$
    – Ian MacDonald
    Jan 7 at 14:17










  • $begingroup$
    If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
    $endgroup$
    – Magic turtle
    Jan 7 at 14:30


















  • $begingroup$
    Sorry my fault, I meant to include that y cannot = 0.
    $endgroup$
    – Magic turtle
    Jan 7 at 14:10










  • $begingroup$
    But can x be 0?
    $endgroup$
    – Ian MacDonald
    Jan 7 at 14:17










  • $begingroup$
    If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
    $endgroup$
    – Magic turtle
    Jan 7 at 14:30
















$begingroup$
Sorry my fault, I meant to include that y cannot = 0.
$endgroup$
– Magic turtle
Jan 7 at 14:10




$begingroup$
Sorry my fault, I meant to include that y cannot = 0.
$endgroup$
– Magic turtle
Jan 7 at 14:10












$begingroup$
But can x be 0?
$endgroup$
– Ian MacDonald
Jan 7 at 14:17




$begingroup$
But can x be 0?
$endgroup$
– Ian MacDonald
Jan 7 at 14:17












$begingroup$
If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
$endgroup$
– Magic turtle
Jan 7 at 14:30




$begingroup$
If x were 0 y would be less than 0 making x + y negative and a negative number cannot be a perfect square
$endgroup$
– Magic turtle
Jan 7 at 14:30



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