Find Inverse of f(x)=\frac{7e^{x}-6}{e^{x}+8}: Solve x

In summary, the conversation discusses finding the inverse of the function f(x)=\frac{7e^{x}-6}{e^{x}+8}. The process involves setting f(x) equal to y and using logarithms to isolate x. The final formula for the inverse is given as y = 7 - \frac{62}{e^x + 8}. It is also suggested to simplify the function before finding the inverse.
  • #1
7yler
31
0
Find a formula for the inverse of f.

f(x)=[tex]\frac{7e^{x}-6}{e^{x}+8}[/tex]

I set f(x) equal to y, and operated on it until I got:

ln(y)=ln(7[tex]e^{x}-6)-ln(e^{x}+8)[/tex]

But I'm stuck. I'm not sure how to isolate x.
 
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  • #2
7yler said:
Find a formula for the inverse of f.

f(x)=[tex]\frac{7e^{x}-6}{e^{x}+8}[/tex]

I set f(x) equal to y, and operated on it until I got:

ln(y)=ln(7[tex]e^{x}-6)-ln(e^{x}+8)[/tex]

But I'm stuck. I'm not sure how to isolate x.

[tex]y = \frac{7e^{x}-6}{e^{x}+8}[/tex]
Multiply both sides by ex + 8 to get

[tex]y(e^x + 8) = 7e^{x}-6[/tex]

Now expand the left side. Then bring all the terms that involve x to the left side, and move all the other terms to the right side.
Solve for x.

The basic idea is that if y = f(x), and f is invertible, then x = f-1(y).

That gives you the inverse function, as a function of y. To write the inverse as a function of x, simply change each occurrence of y in the formula of the inverse to an x.
 
  • #3
That was a huge help. Thank you.
 
  • #4
You might simplify it before you invert rather than after . I think the RHS is

[tex] 7 - \frac{62}{e^x + 8} [/tex]

Something like that anyway.
 

1. What is the inverse of f(x)=\frac{7e^{x}-6}{e^{x}+8}?

The inverse of a function is a function that “undoes” what the original function does. In this case, the inverse of f(x) is denoted as f^{-1}(x) and can be found by solving for x in the original equation.

2. How do I solve for x in the equation f(x)=\frac{7e^{x}-6}{e^{x}+8}?

To solve for x, you will need to use algebraic techniques such as isolating x on one side of the equation, factoring, or using the quadratic formula. In this case, you can start by multiplying both sides of the equation by the denominator, e^{x}+8.

3. Can the inverse of f(x)=\frac{7e^{x}-6}{e^{x}+8} be expressed in terms of elementary functions?

Unfortunately, the inverse of this function cannot be expressed in terms of elementary functions. This means that it cannot be written using basic operations such as addition, subtraction, multiplication, division, and exponentiation.

4. Is there a specific method for finding the inverse of a function?

Yes, there are several methods for finding the inverse of a function. One common method is to switch the x and y variables in the original equation and solve for y. Another method is to use the horizontal line test to determine if the function is one-to-one, which is a necessary condition for a function to have an inverse.

5. Are there any restrictions on the domain of f(x)=\frac{7e^{x}-6}{e^{x}+8} in order for it to have an inverse?

In order for a function to have an inverse, it must be one-to-one, meaning that each input has a unique output. Therefore, there may be restrictions on the domain of the function to ensure that it is one-to-one. In this case, the natural log of (e^{x}+8) must be greater than 0, so the domain must be restricted to x>-8.

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