Question 13
Consider the functions $f$ defined on the set of integers such that
$$
f(x) = f\left(x^{2} + x + 1\right),
$$
for all integers $x$. Find
(a) all even functions,
(b) all odd functions of this kind.
$$
f(x) = f\left(x^{2} + x + 1\right),
$$
for all integers $x$. Find
(a) all even functions,
(b) all odd functions of this kind.