(A) In the formula for function f(x) = (2x^2 + 1)^(1/3) replace x by -x.
You will see that the value f(-x) is the same as the value of f(x).
It means that this function f(x) is even.
(B) In the formula for function g(x) = replace x by -x.
You will see that the value g(-x) is of opposite sign comparing with g(x).
It means that this function g(x) is odd.
By the way, the formula for g(x), after canceling/reducing is
g(x)= 1 for x > 0, g(x) = -1 for x < 0, which also points that g(x) is an odd function.