You can evaluate the functions separately, then add results: .. f(3) = 2*3 +21 = 27 .. g(3) = 3 -24 = -21 (f +g)(3) = f(3) +g(3) = 27 -21 = 6
Or, you can find the combined function and evaluate that for x=3. .. (f +g)(x) = f(x) +g(x) .. = (2x +21) +(x -24) .. = 3x -3 The .. (f +g)(3) = 3*3 -3 = 6