Math Problem Statement

Which of the following is the graph for the inverse of the function f(x) = x^3 + 5x^2 + 1, where x ≥ 0?

Solution

The problem asks for the graph of the inverse of the function f(x)=x3+5x2+1f(x) = x^3 + 5x^2 + 1, where x0x \geq 0. Let’s solve it step by step:


Key Steps:

  1. Understand the function:

    • f(x)=x3+5x2+1f(x) = x^3 + 5x^2 + 1 is a strictly increasing function for x0x \geq 0 (since its derivative f(x)=3x2+10x>0f'(x) = 3x^2 + 10x > 0 for x0x \geq 0).
    • This means f(x)f(x) is one-to-one and has an inverse on this domain.
  2. Graphing the inverse:

    • The graph of an inverse function, f1(x)f^{-1}(x), is the reflection of the original function f(x)f(x) across the line y=xy = x.
    • We will look for a graph that satisfies this reflection symmetry for x0x \geq 0.
  3. Analyze the given options:

    • The correct graph should:
      • Start near (1,0)(1, 0) because f(0)=1f(0) = 1, so the inverse f1(1)=0f^{-1}(1) = 0.
      • Increase steadily and flatten out as xx grows, since f(x)f(x) steepens in this range.

Observing the Options:

After comparing each graph against these criteria:

  • The correct graph is the fourth option, which shows a reflection of f(x)f(x) across y=xy = x, starting near (1,0)(1, 0) and increasing.

Would you like further clarification or additional steps?


Follow-up Questions:

  1. Why is f(x)=x3+5x2+1f(x) = x^3 + 5x^2 + 1 one-to-one on x0x \geq 0?
  2. How can you algebraically verify if a graph reflects across y=xy = x?
  3. What does the derivative f(x)=3x2+10xf'(x) = 3x^2 + 10x tell us about f(x)f(x)'s behavior?
  4. How does restricting x0x \geq 0 affect the graph of the inverse?
  5. Can you find the exact formula for f1(x)f^{-1}(x) algebraically?

Tip:

To visualize inverse functions, always check the symmetry of a function across y=xy = x.

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Math Problem Analysis

Mathematical Concepts

Inverse functions
Graphing functions
Symmetry across y = x

Formulas

f(x) = x^3 + 5x^2 + 1
f'(x) = 3x^2 + 10x

Theorems

The inverse of a function reflects across the line y = x

Suitable Grade Level

Grades 10-12