# function

• Dec 8th 2010, 06:49 PM
sigma1
function
f(x) = 5(2+x) and g(x) = x/5 +7 which maps R into R

$find f^{-1}x = x$

i know how to find $find f^{-1}x$ but am not sure what to so after that.

$f^{-1}x$=
y = x\5 -2
• Dec 8th 2010, 06:52 PM
dwsmith
It looks like you are done. I don't see anything else you are supposed to do unless there is more to the question you didn't post. Do you need to find the inverse of g(x) too?
• Dec 8th 2010, 06:57 PM
sigma1
Quote:

Originally Posted by dwsmith
It looks like you are done. I don't see anything else you are supposed to do unless there is more to the question you didn't post. Do you need to find the inverse of g(x) too?

ok i will post the question in order..

1. find $f^{-1} x$

2.determine the value of x which $f^{-1} x=x$
• Dec 8th 2010, 07:02 PM
dwsmith
$\displaystyle f^{-1}(f(x))=x$
• Dec 8th 2010, 07:12 PM
sigma1
Could you show me how that is done. Am afraId I may interpret it the wrong way. Thanks.
• Dec 8th 2010, 07:14 PM
dwsmith
$\displaystyle f^{-1}(5(2+x))=\frac{5(2+x)}{5}-2=\cdots$
• Dec 8th 2010, 07:24 PM
sigma1
Ok thanks alot
• Dec 9th 2010, 01:39 AM
HallsofIvy
Since you had already determined that [tex]f^{-1}(x)= \frac{x}{5}- 2, determining x such that $f^{-1}(x)= x$ just means solving $\frac{x}{5}- 2= x$.