Math Problem Statement

Consider the functions f and g that are defined for xxR by xf(x)=ex and xg(x)=5x.

Determine the expression of xf−1(x), xg−1(x) and x()gf−1(x)

Solution

Let's determine the inverse functions for f(x)=exf(x) = e^x and g(x)=5xg(x) = 5x, and then find the expression for g(f1(x))g(f^{-1}(x)).

1. Finding f1(x)f^{-1}(x) (the inverse of f(x)=exf(x) = e^x):

To find the inverse function f1(x)f^{-1}(x), we need to solve the equation y=exy = e^x for xx.

y=exy = e^x

Taking the natural logarithm (ln) on both sides:

ln(y)=x\ln(y) = x

So, the inverse function is:

f1(x)=ln(x)f^{-1}(x) = \ln(x)

2. Finding g1(x)g^{-1}(x) (the inverse of g(x)=5xg(x) = 5x):

To find the inverse function g1(x)g^{-1}(x), we solve the equation y=5xy = 5x for xx.

y=5xy = 5x

Dividing both sides by 5:

x=y5x = \frac{y}{5}

So, the inverse function is:

g1(x)=x5g^{-1}(x) = \frac{x}{5}

3. Finding g(f1(x))g(f^{-1}(x)):

We need to compute g(f1(x))g(f^{-1}(x)).

First, substitute f1(x)=ln(x)f^{-1}(x) = \ln(x) into g(x)=5xg(x) = 5x:

g(f1(x))=g(ln(x))=5ln(x)g(f^{-1}(x)) = g(\ln(x)) = 5 \cdot \ln(x)

So, the expression is:

g(f1(x))=5ln(x)g(f^{-1}(x)) = 5\ln(x)

Summary of the results:

  • f1(x)=ln(x)f^{-1}(x) = \ln(x)
  • g1(x)=x5g^{-1}(x) = \frac{x}{5}
  • g(f1(x))=5ln(x)g(f^{-1}(x)) = 5\ln(x)

Would you like more details or have any questions about these calculations?

Here are some related questions to consider:

  1. What is the domain of the inverse function f1(x)=ln(x)f^{-1}(x) = \ln(x)?
  2. How would the expressions change if f(x)=e2xf(x) = e^{2x} instead?
  3. Can you determine f(g1(x))f(g^{-1}(x)) and how it relates to xx?
  4. What are the properties of the compositions f(f1(x))f(f^{-1}(x)) and g(g1(x))g(g^{-1}(x))?
  5. How do these inverses and their compositions affect the graphical interpretation of the functions?

Tip: When finding inverse functions, remember that applying the original function and its inverse in succession will return you to your starting value, i.e., f(f1(x))=xf(f^{-1}(x)) = x and g(g1(x))=xg(g^{-1}(x)) = x.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Functions
Inverse Functions
Exponential Functions
Linear Functions

Formulas

Inverse function formula
Exponential function formula
Linear function formula

Theorems

-

Suitable Grade Level

Grades 11-12