# Thread: Find the F inverse of 6 for a combined function - Algebraically

1. ## Find the F inverse of 6 for a combined function - Algebraically

Hello,

I am stuck with this problem. I can see that the answer is "1" in the graphing calculator but not able to find it algebraically.

Find F-1(6) for F(x)= ex-1+ 2lnx + 5x

Any help will be appreciated.

2. ## Re: Find the F inverse of 6 for a combined function - Algebraically

The inverse of this function cannot be found using elementary algebraic methods ... one has to notice by observation that $f(1)=6 \implies f^{-1}(6)=1$, or use technology as you did.

3. ## Re: Find the F inverse of 6 for a combined function - Algebraically

Thank you so much for your help. Appreciate.