Math Problem Statement

Consider the equation f(x) = x^4 - 32x^2 + 3. Find the intervals where the function is increasing and decreasing, the local extrema, and the inflection points along with the concavity.

Solution

From the image, I can see a problem regarding a polynomial function f(x)=x432x2+3f(x) = x^4 - 32x^2 + 3, with parts (a), (b), and (c) addressing increasing/decreasing intervals, local extrema, and inflection points/concavity. Here's an overview of what the problem entails and how it's solved:

Part (a): Increasing and Decreasing Intervals

The function's derivative, f(x)=4x364xf'(x) = 4x^3 - 64x, determines where f(x)f(x) is increasing or decreasing:

  1. Critical Points: Solve f(x)=0f'(x) = 0, yielding x=4,0,4x = -4, 0, 4.
  2. Analyze f(x)f'(x) sign changes in the intervals: (,4)(-\infty, -4), (4,0)(-4, 0), (0,4)(0, 4), and (4,)(4, \infty).
    • f(x)>0f'(x) > 0 (increasing) in (4,0)(-4, 0) and (4,)(4, \infty).
    • f(x)<0f'(x) < 0 (decreasing) in (,4)(-\infty, -4) and (0,4)(0, 4).

Part (b): Local Extrema

Evaluate f(x)f(x) at the critical points x=4,0,4x = -4, 0, 4:

  • f(4)=253f(-4) = -253, a local minimum.
  • f(0)=3f(0) = 3, a local maximum.
  • f(4)=253f(4) = -253, a local minimum.

Part (c): Inflection Points and Concavity

The second derivative, f(x)=12x264f''(x) = 12x^2 - 64, helps analyze concavity:

  1. Inflection Points: Solve f(x)=0f''(x) = 0, yielding x=±43x = \pm \frac{4}{\sqrt{3}}.
    • Evaluate f(x)f(x) at x=±43x = \pm \frac{4}{\sqrt{3}}: the yy-coordinates for the inflection points need re-calculating.
  2. Concavity Intervals:
    • f(x)>0f''(x) > 0 (concave up) in (,43)(43,)(-\infty, -\frac{4}{\sqrt{3}}) \cup (\frac{4}{\sqrt{3}}, \infty).
    • f(x)<0f''(x) < 0 (concave down) in (43,43)(-\frac{4}{\sqrt{3}}, \frac{4}{\sqrt{3}}).

Additional Questions:

  1. How is the derivative used to classify increasing or decreasing intervals?
  2. Why does x=4x = -4 give a local minimum instead of a maximum?
  3. What role do the inflection points play in determining the graph's shape?
  4. Can you generalize the method to find extrema and concavity for any polynomial?
  5. How do you interpret the intervals of concave up/down geometrically?

Tip: Always cross-check your derivative solutions by substituting back into the original function to verify critical points and inflection behavior.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Critical Points
Concavity Analysis

Formulas

Derivative: f'(x) = 4x^3 - 64x
Second Derivative: f''(x) = 12x^2 - 64

Theorems

First Derivative Test (for Increasing/Decreasing Intervals)
Second Derivative Test (for Concavity and Inflection Points)

Suitable Grade Level

Grades 11-12 or early college