What is the inverse of f(x) = x^3 + 2x?

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SUMMARY

The inverse of the function f(x) = x^3 + 2x cannot be expressed in a simple form. To find the inverse, one must interchange x and y, resulting in the equation x = y^3 + 2y. However, this leads to a complex cubic equation that does not yield a straightforward solution. The discussion emphasizes the necessity of transforming the expression for f(x) into F(y) and solving the cubic equation for x to determine the inverse function.

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tomcenjerrym
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What is the inverse of this function [tex]f(x) = x^3 + 2x[/tex]?

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[tex]f(x) = x^3 + 2x[/tex]

[tex]y = x^3 + 2x[/tex]

interchange [tex]x \Leftrightarrow y[/tex]

[tex]x = y^3 + 2y[/tex]

and it's a dead end to me ...
 
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That will not get you where you need to be. Rather then simply interchanging x and y, you need to chang your expression for f(x) as F(y). A simple example:

f(x)= 3x + 5

y = 3x + 5

y - 5 = 3x

y/3 - 5/3 = x

x = y/3 - 5/3

so now you have x = F(y)
 
What you need to do is solve the equation x3+ 2x= y for x. Thats solving a fairly general cubic equation. Do you have any reason to think that the inverse can be written in a simple form?
 

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