Check the injectivity and surjectivity of the following functions: (1) f: N→N given by f(x) = x²

(2) f: Z→Z given by f(x) = x²
(3) f: R→R given by f(x) = x²
(4) f: N→N given by f(x) = x³
(5) f: Z→Z given by f(x) = x³