Case 3: x >= 2. Therefore 2^x ///0 (mod 4) and z^2/// 0,1 (mod 4), which implies that
11^y /// 0, 1 (mod 4).It can be observed that if y is an odd non-negative integer, then
11^y /// 3 (mod 4). Therefore, y is an even non-negative integer. Let y = 2k for some non-negative
integer k. Thus,