Find f X g , g X f , and f X f

Question

f(x) = 3sqrt x-1 g(x) = x^3 + 1

For f(x) the 3 is little above the sqrt sign.

My answers were:

f(g(x)) = 3sqrt x^3 + 1 -1
g(f(x)) = 3sqrt (x-1)^3 -1
f(f) = 3sqrt x-1-1

My teacher said these were wrong. Please help. I do not know how to correct these. Thank you!