Adding some constant k to a function f(x) has the effect of shifting the graph of the function up by k units. To find what k is, we can pick one point on f(x) and see how far up it's been shifted on the graph of g(x). Looking at the point (0, 2) on f(x), we notice that the point at the same x-coordinate on g(x) is (0, 5) - it's been shifted up 3 units (since the distance between 2 and 5 is 5 - 2 = 3), so we can say that g(x) = f(x) + 3, making k = 3.
