For a technically-correct solution (if your course requires that you "show your work"), just follow the formula they gave you in your book: Plug "-x" in for every "x", and simplify. If you end up with f(x) (that is, with exactly what you started with), then the function is even; if you end up with -f(x) (that is, with the same thing, but with all the signs changed), then the function is odd; otherwise, the function is neither.
Eliz.