You may want to review operations on functions first.

If you're asked for (f + g)(x), that's even easier. You just add the expressions for f and for g. For example, if f(x) = −2x2 + 2 and g(x) = x, then (f + g)(x) = −2x2 + 2 + x. Of course, in general you'll need to use the rules for adding, subtracting, multiplying or dividing polynomials, or rational functions, or whatever.