Sum of Two Squares: Can $5^{64}-3^{64}$ Be Written?

In summary, the sum of two squares is a mathematical expression in the form of a² + b², where a and b are integers. Not all numbers can be written as the sum of two squares, only those with prime factors congruent to 1 modulo 4. The expression $5^{64}-3^{64}$ is a perfect example of a number that can be written as the sum of two squares. To determine if a number can be written as the sum of two squares, we need to factor it and check if its prime factors are congruent to 1 modulo 4. There is a formula, the Brahmagupta-Fibonacci identity, for finding the two squares that make up the sum of a given
  • #1
anemone
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Is it possible to write $5^{64}-3^{64}$ as the sum of two squares?
 
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  • #2
anemone said:
Is it possible to write $5^{64}-3^{64}$ as the sum of two squares?

$5^{64}-3^{64}$
=$(5^{32}+3^{32})(5^{16}+3^{16})(5^8+3^8)(5^4+3^4)(5^2+3^2)(5+3)(5-3)$
= $16((5^{32}+3^{32})(5^{16}+3^{16})(5^8+3^8)(5^4+3^4)(5^2+3^2)$
= $4^2((5^{32}+3^{32})(5^{16}+3^{16})(5^8+3^8)(5^4+3^4)(5^2+3^2)$

as product of 2 numbers both sum of 2 squares can be represented as sum of 2 squares and 4^2 is a square so argument repeatedly we have the ans Yes
 
  • #3
I'm not familiar with this theorem. Are you saying that any form \(\displaystyle (a^{2p} + b^{2p})(c^{2q} + d^{2q} )(e^{2r} + f^{2r})\) can always be written as the sum of two squares? Or do we additionally need c = e =a, d = f = b or something?
-Dan
 
  • #4
topsquark said:
I'm not familiar with this theorem. Are you saying that any form \(\displaystyle (a^{2p} + b^{2p})(c^{2q} + d^{2q} )(e^{2r} + f^{2r})\) can always be written as the sum of two squares? Or do we additionally need c = e =a, d = f = b or something?
-Dan
[sp]
The identity $(a^2+b^2)(c^2+d^2) = (ac+bd)^2 + (ad-bc)^2$ shows that a product of sums of two squares is also a sum of two squares.
[/sp]
 
  • #6
Thanks Kali for your solution!

And thanks to Opalg too for explaining thing for topsquark! I appreciate that!
 

FAQ: Sum of Two Squares: Can $5^{64}-3^{64}$ Be Written?

What is the sum of two squares?

The sum of two squares is a mathematical expression in the form of a² + b², where a and b are integers. This is also known as a Pythagorean triple, representing the sides of a right triangle.

Can all numbers be written as the sum of two squares?

No, not all numbers can be written as the sum of two squares. Numbers that are not themselves perfect squares can only be written as the sum of two squares if they have prime factors that are congruent to 1 modulo 4.

What is the significance of $5^{64}-3^{64}$ in relation to sum of two squares?

The expression $5^{64}-3^{64}$ is significant because it is a perfect example of a number that can be written as the sum of two squares. Both 5 and 3 are prime numbers congruent to 1 modulo 4, making it possible for them to be written as the sum of two squares.

How can we determine if a number can be written as the sum of two squares?

To determine if a number can be written as the sum of two squares, we need to factor it and check if its prime factors are congruent to 1 modulo 4. If all prime factors meet this condition, then the number can be written as the sum of two squares.

Is there a formula for finding the two squares that make up the sum of a given number?

Yes, there is a formula known as the Brahmagupta-Fibonacci identity that can be used to find the two squares that make up the sum of a given number. It states that for any integer n, the sum of two squares can be found by taking the square root of n and then finding the closest integer to it, and then finding the difference between n and the square of that integer.

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