Marshall's mistake is that he is only considering a small portion of the domains of the functions. Specifically, the correct response is:
Marshall is only considering a small portion of the domains of the functions. If he went farther to the right on the graph, he would observe that the growth rate of f(x)=6(1.5)x eventually surpasses the growth rate of g(x)=5x+10 for large values of x.
This reflects the fact that while \( g(x) \) is a linear function and grows at a constant rate, the exponential function \( f(x) = 6(1.5)^x \) will eventually grow faster than the linear function as \( x \) becomes larger.