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I need to get the inverse of that function. Can I get some help please? Thanks!

$$ f(x) = -x^5-2x+2 $$

Alex
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    ...maybe you just have to show that it has one? – JP McCarthy Aug 29 '13 at 14:01
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    To show the existence, prove that the derivative is nonzero for all $x$. – AlexR Aug 29 '13 at 14:09
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    Solutions can be expressed in terms of the Bring radical, which in turn can be expanded as a Taylor series or expressed in terms of hypergeometric functions. Is that what you really want? – hardmath Aug 29 '13 at 14:12
  • Well, I know it exists, but I need to calculate a value of y out of the inverse, and plugging it in for y in the original equation doesn't seem to like me >: – Alex Aug 29 '13 at 14:16
  • What do you mean by "calculate a value of $y$ out of the inverse"? Please be specific. – Cameron Buie Aug 29 '13 at 14:17
  • Well, I need to find inverse f(4). – Alex Aug 29 '13 at 14:19
  • Do you mean $f^{-1}(4)$? Or do you mean $f^{-1}\bigl(f(4)\bigr)$? The second one is easy. The first one is a pain, and you probably need to take the approach that @hardmath suggested. – Cameron Buie Aug 29 '13 at 14:22
  • The first one. Alright then. I guess I'll do that. Thanks – Alex Aug 29 '13 at 14:24
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    Unless you are specifically on a course discussing the use of hypergeometric series, no sane teacher will ask you to do this in closed form. Approximate solution (Newton-Rhapson) is possible, if that's ok. Depends on the context. – Jyrki Lahtonen Aug 29 '13 at 14:40
  • Maybe you are supposed to find $f^{-1}(4)$ numerically. This is much less than finding the inverse of function $f$. – GEdgar Aug 29 '13 at 14:47

1 Answers1

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Hint : $f^{-1}(4)=-$0.81747101900096663171875403718014803062393890731658574158584124817593022421784472707737900090539978006430155207367922222188742819732555540345960429125640051835653129488424662383631508425805621121882571...

Xoff
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