Which of these is a solution to x2+y2=2z2x^2 + y^2 = 2z^2x2+y2=2z2 where (x,y,z)=(1,7,5)(x, y, z) = (1, 7, 5)(x,y,z)=(1,7,5)?
Yes, it is a solution
No, it is not
Only if x=yx=yx=y
Only if x,yx, yx,y are even