ELI5: Explain Like I'm 5

Dixon's identity

Okay, kiddo, let me explain Dixon's identity to you in a really simple way.

Dixon's identity is like a cool math trick that helps us find out if a certain number can be written as the sum of three squares.

Imagine you have a toy box with three little compartments. You want to find out if you can put a certain number of toys inside the toy box using these three compartments, so that each compartment has a certain number of toys.

Well, Dixon's identity helps us do something similar. It tells us that if we take a certain number and multiply it by 4, and then subtract 3 different squares of other numbers, we can find out if the original number can be written as the sum of three squares.

For example, let's say we have the number 29. We can apply Dixon's identity and say:

4 * 29 = 116

Now, let's try to subtract three squares of different numbers from it and see if we get any whole numbers.

We can try:

- 7^2 = 49
- 2^2 = 4
- 2^2 = 4

If we subtract these squares from 116, we get:

116 - 49 - 4 - 4 = 59

Now, 59 is not a perfect square, so we know that 29 cannot be written as the sum of three squares.

And that's how Dixon's identity works! It's a really handy math trick that can help us figure out certain things about numbers. Cool, huh?