# Thread: find the inverse of a function

1. ## find the inverse of a function

it's given that f(x) = v^5 + v^3 + v. So I need to find inverse of (3) and f(f inverse of 2).
I figured out the first, which is relatively easy.
v^5 + v^3 + v = 3, where i get v = 1. So inverse of (3) is 1.

But how do I go about the second part? I know that first I should find the inverse of (2) and then find f(x).

2. ## Re: find the inverse of a function

Originally Posted by Taurus3
it's given that f(x) = v^5 + v^3 + v. So I need to find inverse of (3) and f(f inverse of 2).
I figured out the first, which is relatively easy.
v^5 + v^3 + v = 3, where i get v = 1. So inverse of (3) is 1.

But how do I go about the second part? I know that first I should find the inverse of (2) and then find f(x).
You're expecetd to know that $\displaystyle f(f^{-1}(x)) = x$ by definition.

3. ## Re: find the inverse of a function

huh? But isn't that just the definition?

4. ## Re: find the inverse of a function

Yes and that's exactly what you need, $\displaystyle f(f^{-1}(2))=...$?