8. Find the inflection points of the graph of f(x) = x – 6x², and state the intervals on which the graph of ƒ is concave up and the intervals on which the graph is concave down.
8. Find the inflection points of the graph of f(x) = x – 6x², and state the intervals on which the graph of ƒ is concave up and the intervals on which the graph is concave down.
Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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![### Problem 8: Analyzing Inflection Points and Concavity Intervals
#### Problem Statement
Find the inflection points of the graph of \( f(x) = x^4 - 6x^2 \), and state the intervals on which the graph of \( f \) is concave up and the intervals on which the graph is concave down.
#### Explanation
To solve this problem, you need to follow these steps:
1. **Find the Second Derivative**: Calculate the first and second derivatives of \( f(x) \).
2. **Determine Inflection Points**: Set the second derivative equal to zero and solve for \( x \). These are potential inflection points.
3. **Test Intervals**: Analyze the sign of the second derivative on the intervals determined by these points to establish concavity.
#### Solution Steps
1. **First Derivative**:
\[ f'(x) = \frac{d}{dx}(x^4 - 6x^2) = 4x^3 - 12x \]
2. **Second Derivative**:
\[ f''(x) = \frac{d}{dx}(4x^3 - 12x) = 12x^2 - 12 \]
3. **Finding Inflection Points**:
Set \( f''(x) = 0 \):
\[ 12x^2 - 12 = 0 \]
\[ x^2 = 1 \]
\[ x = \pm 1 \]
Therefore, the potential inflection points are \( x = 1 \) and \( x = -1 \).
4. **Test the Sign of \( f''(x) \)** on intervals \( (-\infty, -1) \), \( (-1, 1) \), and \( (1, \infty) \):
- For \( x < -1 \):
\[ f''(x) = 12x^2 - 12 > 0 \]
So, \( f \) is concave up on \( (-\infty, -1) \).
- For \( -1 < x < 1 \):
\[ f''(x) = 12x^2 - 12 < 0 \]
So, \( f \) is concave down on \( (-1](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fcba7b9ea-03da-4ccc-8cbf-1d9caf29b38a%2Faa4f1c41-b5b5-4b3b-8e2a-ede910a4376c%2Fl7dmm1f_processed.png&w=3840&q=75)
Transcribed Image Text:### Problem 8: Analyzing Inflection Points and Concavity Intervals
#### Problem Statement
Find the inflection points of the graph of \( f(x) = x^4 - 6x^2 \), and state the intervals on which the graph of \( f \) is concave up and the intervals on which the graph is concave down.
#### Explanation
To solve this problem, you need to follow these steps:
1. **Find the Second Derivative**: Calculate the first and second derivatives of \( f(x) \).
2. **Determine Inflection Points**: Set the second derivative equal to zero and solve for \( x \). These are potential inflection points.
3. **Test Intervals**: Analyze the sign of the second derivative on the intervals determined by these points to establish concavity.
#### Solution Steps
1. **First Derivative**:
\[ f'(x) = \frac{d}{dx}(x^4 - 6x^2) = 4x^3 - 12x \]
2. **Second Derivative**:
\[ f''(x) = \frac{d}{dx}(4x^3 - 12x) = 12x^2 - 12 \]
3. **Finding Inflection Points**:
Set \( f''(x) = 0 \):
\[ 12x^2 - 12 = 0 \]
\[ x^2 = 1 \]
\[ x = \pm 1 \]
Therefore, the potential inflection points are \( x = 1 \) and \( x = -1 \).
4. **Test the Sign of \( f''(x) \)** on intervals \( (-\infty, -1) \), \( (-1, 1) \), and \( (1, \infty) \):
- For \( x < -1 \):
\[ f''(x) = 12x^2 - 12 > 0 \]
So, \( f \) is concave up on \( (-\infty, -1) \).
- For \( -1 < x < 1 \):
\[ f''(x) = 12x^2 - 12 < 0 \]
So, \( f \) is concave down on \( (-1
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