I'm stumped on this.

New problem!

Original:

x^2 + (x+5)^2 =(5√5)^2

Now, I tried canceling out the radical. That gives me "0" for C when factoring, though, so it doesn't work out ( I believe).

Doing 5^2 * 5 gives me 625, which gives me x=-20, 15 after factoring. Doesn't check out.