The given function is:

f(x) =

It's asking for f'(x) = and says the answer will involve the variables t and x.

I found the derivative of the function using the Quotient Rule, but I don't understand the part where I need to take the limit which will include the variables t and x. Then it says taking the limit of that fractional expression gives f'(x) = _______. Wouldn't you have already found that in the first part of the question?