The first one is correct, because when you differentiate (x+1), you got 1, whereas when you got to differentiate (3x^3), you have 9x², which should appear in f '(x).
Because you have a composite function and you didn't use the chain rule. either use the chain rule for the second question or using the rules of indices.
Because you have a composite function and you didn't use the chain rule. either use the chain rule for the second question or using the rules of indices.
We haven't learned any of those yet! Only power, product, and quotient rules!!