This may be a quite basic problem, but I've been looking for a long time for a solution and could not find any.

Let's assume I have a function:

f:=(x)->exp(a*x);

Now I do diff(f(x), x);

How to make maple return result in a form: f(x)*a instead of a*exp(a*x)?

Ofcourse I would be very grateful for a solution which can do the same with nested functions and expressions...