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I'm doing some work on finding the derivative of an inverse function and getting a bit lost, probably because I am confusing myself with the inverses. So i think i need to clear up the inverse part before I move on to the calculus bit.

You have the function

f(x) = 1/3x^{3}- x^{2}+ 5x -11

This function has an inverse f^{-1}(x). Set this equal to y

y = f^{-1}(x)

You can then say f(y) = x

Is this because f(y) = f(f^{-1}(x)) = x

I'm now getting confused, due to notation I think. The f by definition is

1/3(some input)^{3}- (some input)^{2}+ 5(some input) -11

So f(y) = 1/3y^{3}- y^{2}+ 5y -11 = x

Is this right?

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# Homework Help: Confused about an inverse (which then leads on to a calculus problem)

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