For each function below enter the letter E if the function is even, the letter O if it's odd, and the letter N if it's neither even nor odd.
$f(x) = x^4+x^2.$
$f(x) = x^5+x^3.$
$f(x) = x^4 + x^5.$
$f(x) = |x|.$
$f(x) = |x|^3.$
$f(x) = \frac{x^2}{x^2+1}.$
HINT: If in doubt, evaluate the functions at pairs of numbers like $1$ and $and$-1).