# inverse function problem

• Aug 25th 2010, 09:00 AM
juventinoalex
inverse function problem
Could someone explain how to find the inverse function of g(x)=(e^x)-4?

Thanks,
Alex
• Aug 25th 2010, 09:02 AM
Ackbeet
Do you know the general procedure? What ideas have you had so far?
• Aug 25th 2010, 09:03 AM
spycrab
Quote:

Originally Posted by juventinoalex
Could someone explain how to find the inverse function of g(x)=(e^x)-4?

Thanks,
Alex

First change g(x) to y=
$y=e^{x}-4$
solve for x, and then switch the x and y terms
• Aug 25th 2010, 12:07 PM
juventinoalex
Yes, i did that up to the solve for x part. I just did a problem where the x wasn't an exponent but that part has me kind of confused.
• Aug 25th 2010, 12:21 PM
HallsofIvy
So what, exactly have you done? Did you get to $e^x= y+ 4$?

Do you know that the inverse to $e^x$ is ln(x)?

Here's another way of looking at it: $f(x)= e^x- 4$ basically tells you to do two things to x to evaluate the function: first take the exponential, then subtract 4. To find the inverse do the opposite things in the opposite order. Since the last thing you do in evaluating the function is "subtract 4", the first thing you do in finding the inverse is "add 4". Since the first thing you do in evaluating the function is take the exponential, the last ting you do in finding the inverse is the opposite of that. What function is the inverse to $e^x$ again?