Answer:
Adding two functions is like plotting one function and taking the graph of that function as the new x-axis. Points of the second function are then plotted with respect to the new axis. For example, (2, 3) becomes "over 2," "up 3 from the new axis," or (3, f + 2).
Another Example:
To add or subtract functions, just add or subtract the values at each point where it makes sense. If the functions are given by formulas, you can just add or subtract the formulas (it doesn't matter whether you plug in values before or after).
Explanation:
Hope this helps. :)