You plug in (-x) and see whether the resulting expression is the negative of f(x), the same as f(x), or neither.
If it's the negative of f(x), then f(x) is odd.
If it's the same as f(x), then f(x) is even.
If it's neither, then f(x) is neither.
(-x)^4 = x^4
sin(2*-x) = sin(-2x) = -sin(2x)
If it's the negative of f(x), then f(x) is odd.
If it's the same as f(x), then f(x) is even.
If it's neither, then f(x) is neither.
(-x)^4 = x^4
sin(2*-x) = sin(-2x) = -sin(2x)