# Math Help - Instanteous Rate of Change

1. ## Instanteous Rate of Change

Hi,
I'm studying for my test right now, and I was thinking of possible questions that might be on the test... and then I came up with a question but I can't answer it. How could I possibly calculate the instanteous rate of change of an exponential function without graphing it?
Thanks for the input.

2. $\frac{d}{dx} (a^x) = a^x \cdot \ln{a}$

3. How would I find it if my function was 4^x for example?
Thanks again.

4. substitute 4 for a