1. The problem statement, all variables and given/known data If d/dx(f(x)) = g(x) and d/dx(g(x)) = f(x2), then d2/dx2(f(x3)) = a) f(x6) b) g(x3) c) 3x2*g(x3) d) 9x4*f(x6) + 6x*g(x3) e) f(x6) + g(x3) 2. Relevant equations 3. The attempt at a solution The answer is D. Since d/dx(f(x)) = g(x), I said that d/dx(f(x3)) should equal 3x2*g(x3), then I took the derivative again and first used product rule so 6x*g(x3) + 3x2*f(x6)*6x5 since you would need to do chain rule again but that doesn't match up with the answer. I've been trying to play around with it for a while and it's just not coming out as the answer.