Help finding a inverse function

In summary, two equations are given, f(x)=2x^3+5x+3 and f^-1(x)=1, and f(x)=x^3/(x^2+1) and f^-1(x)=2. The goal is to find the value of x for each equation. The process of finding explicit forms for the equations may be challenging, but it is not necessary. Instead, one can use the fact that if f^-1(x)=1, then x=f(1). There are formulas for cubic and quartic equations, but they are too complex for practical use. For equations of fifth degree or higher, there are no formulas except in special cases, proven by Galois theory.
  • #1
farmd684
49
0

Homework Statement


Given that f(x)=2x^3+5x+3 and f^-1(x)=1 then find the value of x
Given that f(x)=x^3/(x^2+1) and f^-1(x)=2 then find the value of x

Homework Equations



I got to the eqn x=2Y^3+5Y+3 & X=Y^3/(Y^2+1)


The Attempt at a Solution



But now i m in trouble finding the f^-1(x) in explicit form to use the value of f^-1(x)
 
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  • #2
You are going to have a hard time finding explicit forms. But you don't have to. If e.g. f^(-1)(x)=1, then x=f(1), yes?
 
  • #3
Thanks that got my problem solved :D
But i m just curious to know how to find that big cubic or quadratic functions in explicit mode :)
 
  • #4
If it cubic or quartic, there are formulas, but they are too complicated for most practical uses. If it's fifth degree or worse there are no formulas, except in special cases. There are proofs of this, it's called Galois theory.
 

Related to Help finding a inverse function

What is an inverse function?

An inverse function is a function that reverses the output of another function. In other words, if the original function takes x as an input and produces y as an output, the inverse function takes y as an input and produces x as an output.

Why do we need to find the inverse of a function?

Finding the inverse of a function can be useful in solving equations and understanding the relationship between two variables. It can also help in simplifying complex functions and making them easier to work with.

How do you find the inverse of a function?

To find the inverse of a function, you can follow these steps:

  • Replace the function notation with y.
  • Switch the x and y variables in the equation.
  • Solve for y to get the inverse function.

What is the process for verifying that a function and its inverse are correct?

To verify that a function and its inverse are correct, you can use the horizontal line test. This test involves drawing horizontal lines on the original function and its inverse. If the lines intersect the function at only one point and the inverse at the same point, then the functions are correct inverses of each other.

Are all functions invertible?

No, not all functions are invertible. A function must pass the horizontal line test and have a one-to-one relationship between its input and output in order to have an inverse function. Functions that fail the horizontal line test are not invertible.

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