# Thread: How to take limits of inverse functions!

1. ## How to take limits of inverse functions!

]How would you solve

lim as x -> infinity f-1( x2 + 2 x + 1)

?

Thanks!

2. ## Re: How to take limits of inverse functions!

Why not just find $f^{-1} (x^2+2x+1)$ ?

3. ## Re: How to take limits of inverse functions!

$f(x) = x^2 +2x + 1 = (x+1)^2$

restricting the domain of f(x) to x > -1

$f^{-1}(x) = \sqrt{x} - 1$

the inverse is unbounded as $x \to \infty$

I'm hoping you don't have confusion between inverse and reciprocal functions.

4. ## Re: How to take limits of inverse functions!

What you wrote was $\lim_{x\to\infty} f^{-1}(x^2+ 2x+ 1)$ which we cannot help you with because you did not tell us what "f" is. Skeeter assumed you meant that $f(x)= x^2+ 2x+ 1$ and that you want to find $\lim_{x\to\infty} f^{-1}(x)$. Is that correct?

5. ## Re: How to take limits of inverse functions!

Originally Posted by HallsofIvy
What you wrote was $\lim_{x\to\infty} f^{-1}(x^2+ 2x+ 1)$ which we cannot help you with because you did not tell us what "f" is. Skeeter assumed you meant that $f(x)= x^2+ 2x+ 1$ and that you want to find $\lim_{x\to\infty} f^{-1}(x)$. Is that correct?
that is another reason for my final statement ...

6. ## Re: How to take limits of inverse functions!

I'm interested to know why this Algebra/Pre Calculus question was posted in Statistics...

7. ## Re: How to take limits of inverse functions!

Originally Posted by Prove It
I'm interested to know why this Algebra/Pre Calculus question was posted in Statistics...
not like it matters anymore ... the new owner/moderator hasn't been around for awhile. just note how many problems have been posted in the lobby.