Answer: k = 2
Pick an x value like x = 2
Note that f(2) = 1 and g(2) = 2. This shows we've doubled the f(x) value to get g(x). Therefore k = 2.
Or you could pick on x = 4 to see f(4) = 2 and g(4) = 4. The output of f(x) has been doubled as well.
It doesn't matter what x is since we'll have this doubling effect go on. I recommend picking x values where the points on the blue graph land perfectly on a grid location. Something like x = 5 seems a bit tricky.
