Answer
See image:
Work Step by Step
Work done in desmos.com (online graphic calculator)
The graph of f is red, dashed,
th graph of g is blue, dotted.
Note that the domain of (f+g) is the intersection of the domains of f and g, which, in this case, is the whole set of real numbers.
The yellow arrows are examples showing
that the y-coordinate on the graph of f increases (or decreases) by the amount : g(x),
resulting with a point on the graph of (f+g).