# find inverse function

• Oct 13th 2009, 08:15 AM
absvalue
find inverse function
$f(x) = 5(x-2)^3 - 6$

Could someone help me find the inverse function for this function?

I understand these steps:

Set f(x) to y
$y = 5(x-2)^3 - 6$

Swap x and y
$x = 5(y-2)^3 - 6$

I think I'm supposed to solve for Y, but I'm not sure how to continue.
• Oct 13th 2009, 08:22 AM
skeeter
Quote:

Originally Posted by absvalue
$f(x) = 5(x-2)^3 - 6$

Could someone help me find the inverse function for this function?

I understand these steps:

Set f(x) to y
$y = 5(x-2)^3 - 6$

Swap x and y
$x = 5(y-2)^3 - 6$

I think I'm supposed to solve for Y, but I'm not sure how to continue.

$x = 5(y-2)^3 - 6$

add 6 to both sides ...

$
x+6 = 5(y-2)^3
$

divide both sides by 5 ...

$
\frac{x+6}{5} = (y-2)^3
$

take the cube root of both sides ...

$
\sqrt[3]{\frac{x+6}{5}} = y-2
$

add 2 to both sides ...

$
\sqrt[3]{\frac{x+6}{5}} + 2 = y
$

you're done.
• Oct 13th 2009, 08:23 AM
statmajor
$x = 5(y-2)^3 - 6$

So far you are right. Like you said, you need to solve for y, and you just need some basic algebra to do that.

$x + 6 = 5(y-2)^3$
• Oct 13th 2009, 09:08 AM
Raoh
hi(Happy)
$(y-2)^{3}=\frac{x+6}{5}\Leftrightarrow y-2=\sqrt[3]{\frac{x+6}{5}}\Leftrightarrow y= \sqrt[3]{\frac{x+6}{5}}+2$,now change $y$ to $f^{-1}(x)$