Even and odd functions

A function f on R is an even function if for all x in the domain of f,

f(x) = f(-x).

Such a function is symmetric with respect to the y-axis when graphed.

A function f on R is an odd function if for all x in the domain of f,

-f(x) = f(-x).

Such a function has rotational symmetry with respect to the origin.

Examples

$x^2$ is a even function but $x^3$ is odd. $X^5 +56x+909$ is neither.