Math Problem Statement

Let f and g be functions that are differentiable everywhere. If g is the inverse function of f and if g(-2) = 5 and f'(5) = -1/2, then g'(-2) = ?

Solution

The problem states:

Let ff and gg be functions that are differentiable everywhere. If gg is the inverse function of ff and g(2)=5g(-2) = 5, and f(5)=12f'(5) = -\frac{1}{2}, then find g(2)g'(-2).

Solution:

Since gg is the inverse of ff, we use the formula for the derivative of the inverse function: g(x)=1f(g(x))g'(x) = \frac{1}{f'(g(x))}

Given:

  • g(2)=5g(-2) = 5
  • f(5)=12f'(5) = -\frac{1}{2}

Substitute x=2x = -2 into the inverse derivative formula:

g(2)=1f(g(2))g'(-2) = \frac{1}{f'(g(-2))}

Since g(2)=5g(-2) = 5, this simplifies to:

g(2)=1f(5)g'(-2) = \frac{1}{f'(5)}

Substituting f(5)=12f'(5) = -\frac{1}{2}:

g(2)=112=2g'(-2) = \frac{1}{-\frac{1}{2}} = -2

Answer:

2\boxed{-2}

Would you like more details or have any other questions?

Here are some related questions to explore:

  1. How do you find the derivative of an inverse function in general?
  2. What is the geometric interpretation of the inverse function's derivative?
  3. How do we interpret the signs of f(x)f'(x) and g(x)g'(x) in terms of function behavior?
  4. What are the conditions for a function to have an inverse function?
  5. Can the formula g(x)=1f(g(x))g'(x) = \frac{1}{f'(g(x))} be used if f(g(x))=0f'(g(x)) = 0? Why or why not?

Tip: Always check that the derivative f(g(x))f'(g(x)) is non-zero when using the inverse function derivative formula to avoid undefined expressions.

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Math Problem Analysis

Mathematical Concepts

Calculus
Inverse Functions
Derivatives

Formulas

g'(x) = 1 / f'(g(x))

Theorems

Inverse Function Theorem

Suitable Grade Level

Grades 11-12 (High School Calculus)