Math Problem Statement

use this photo for the rules

Use this photo for the rules.

Solution

Based on the rules provided in the photo, here's how we can analyze a function using critical points, the first derivative test, and the second derivative test.


Example Problem:

Analyze f(x)=x33x2+2f(x) = x^3 - 3x^2 + 2 to determine:

  1. The critical points of f(x)f(x),
  2. Whether these points are local maxima, minima, or neither,
  3. Any potential inflection points.

Step 1: Find the critical points (f(x)=0f'(x) = 0)

The function is f(x)=x33x2+2f(x) = x^3 - 3x^2 + 2. Compute the first derivative: f(x)=3x26xf'(x) = 3x^2 - 6x

Factorize f(x)f'(x): f(x)=3x(x2)f'(x) = 3x(x - 2)

Set f(x)=0f'(x) = 0 to find the critical points: 3x(x2)=0    x=0orx=23x(x - 2) = 0 \quad \implies \quad x = 0 \quad \text{or} \quad x = 2

The critical points are at x=0x = 0 and x=2x = 2.


Step 2: Use the second derivative test to classify critical points

Compute the second derivative: f(x)=6x6f''(x) = 6x - 6

Evaluate f(x)f''(x) at each critical point:

  • For x=0x = 0: f(0)=6(0)6=6(negative, so a local maximum at x=0).f''(0) = 6(0) - 6 = -6 \quad (\text{negative, so a local maximum at } x = 0).

  • For x=2x = 2: f(2)=6(2)6=6(positive, so a local minimum at x=2).f''(2) = 6(2) - 6 = 6 \quad (\text{positive, so a local minimum at } x = 2).


Step 3: Identify inflection points

To find potential inflection points, solve f(x)=0f''(x) = 0: 6x6=0    x=16x - 6 = 0 \quad \implies \quad x = 1

Check the sign change of f(x)f''(x) around x=1x = 1:

  • For x<1x < 1 (e.g., x=0x = 0): f(0)=6f''(0) = -6 (negative).
  • For x>1x > 1 (e.g., x=2x = 2): f(2)=6f''(2) = 6 (positive).

Since f(x)f''(x) changes sign, x=1x = 1 is an inflection point.


Summary of Results:

  1. Critical points:

    • x=0x = 0: Local maximum (f(0)=2f(0) = 2).
    • x=2x = 2: Local minimum (f(2)=2f(2) = -2).
  2. Inflection point:

    • x=1x = 1: Inflection point (f(1)=0f(1) = 0).

Would you like to attempt a similar question or see this visualized on a graph?


Related Questions:

  1. How would the critical points change for f(x)=x44x3+6x21f(x) = x^4 - 4x^3 + 6x^2 - 1?
  2. Can you classify the nature of x=0x = 0 and x=2x = 2 without using the second derivative test?
  3. What are the implications of f(x)=0f''(x) = 0 for concavity and inflection points?
  4. How does the first derivative test compare to the second derivative test in this case?
  5. Can you compute the derivative of g(x)=x33x2+ln(x)g(x) = x^3 - 3x^2 + \ln(x) and analyze it?

Tip:

When applying the second derivative test, remember that if f(x)=0f''(x) = 0, the test is inconclusive, and the first derivative test may be needed for clarification.

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Math Problem Analysis

Mathematical Concepts

Calculus
Critical Points
First Derivative Test
Second Derivative Test
Inflection Points

Formulas

First derivative test: f'(x) = 0 to find critical points
Second derivative test: f''(x) < 0 for local maxima, f''(x) > 0 for local minima
Inflection points: Ensure sign(f''(x - ε)) ≠ sign(f''(x + ε))

Theorems

First Derivative Test
Second Derivative Test
Inflection Point Criteria

Suitable Grade Level

Grades 11-12