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Mathematics 18 Online
OpenStudy (anonymous):

find inverse

OpenStudy (anonymous):

f(x)= 8/ (x-3)^2

OpenStudy (anonymous):

solve \[x=\frac{8}{(y-3)^2}\] for \(y\) in a few steps

OpenStudy (anonymous):

\[(y-3)^2=\frac{8}{x}\] \[y-3=\pm\sqrt{\frac{8}{x}}\] \[y=3\pm\sqrt{\frac{8}{x}}\]

OpenStudy (anonymous):

How about this one ? (x-1)^3 / 8

OpenStudy (anonymous):

@zepdrix plz help

OpenStudy (anonymous):

find inverse @zepdrix

OpenStudy (anonymous):

i did it but my answer came out different form the book :(

zepdrix (zepdrix):

\[\large y=\frac{(x-1)^3}{8}\]So we start by swapping the x and y,\[\large x=\frac{(y-1)^3}{8}\]Let's multiply both sides by 8,\[\large 8x=(y-1)^3\]Take the cube root of both sides,\[\large \sqrt[3]{8x}=y-1\]Add 1 to each side,\[\large y=\sqrt[3]{8x}+1\]8 is a perfect square, let's go ahead and pull that out of the root. And I'm also going to write the x using a rational expression, it just looks nicer that way :)\[\large f^{-1}(x)=8x^{1/3}+1\]

zepdrix (zepdrix):

Luckily we don't need to worry about adding a \(\large \pm\) to this root, since it's an `odd` root.

zepdrix (zepdrix):

Woops, sorry i pulled the 8 out and I didn't take the root LOL

OpenStudy (anonymous):

oh cube root.... i see

zepdrix (zepdrix):

\[\large f^{-1}(x)=2x^{1/3}+1\] The cube root of 8 is 2, sorry lil typo there :3

zepdrix (zepdrix):

Yah you had a 3rd power, so you need to take the 3rd root in order to clean that up :)

OpenStudy (anonymous):

on the back of the book, it just took the 2 from the 8 2√x +1

OpenStudy (anonymous):

i don't know how to do that cube root so...lol

zepdrix (zepdrix):

hmm

OpenStudy (anonymous):

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