#117. (a) Prove that the only solution in integers of the equation \[x^2 + y^2 + z^2 = 2xyz\] is \(x = y = z = 0\).

(b) Find the integers \(x, y, z, v\) such that \[x^2 + y^2 + z^2 + v^2 = 2xyzv.\]