Find the intervals on which f(x) = -2(x + 3.5)(x – 0.5)(x – 3) is positive by plotting a graph. f(x) is positive on

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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### Finding Intervals of Positivity for a Given Function

**Problem Statement:**
You are given the function:

\[ f(x) = -2(x + 3.5)(x - 0.5)(x - 3) \]

Your task is to find the intervals on which \( f(x) \) is positive by plotting a graph.

#### Steps to Determine Intervals of Positivity:
1. **Identify Critical Points:**
   - Find the roots of the function where \( f(x) = 0 \).
     For the given function:
     \[
     x + 3.5 = 0 \implies x = -3.5
     \]
     \[
     x - 0.5 = 0 \implies x = 0.5
     \]
     \[
     x - 3 = 0 \implies x = 3
     \]
   The critical points are \( x = -3.5 \), \( x = 0.5 \), and \( x = 3 \).

2. **Plot the Graph:**
    - Sketch the polynomial function on a graph considering the critical points.
    - Determine where the function crosses the x-axis: at \( x = -3.5 \), \( x = 0.5 \), and \( x = 3 \).
    - The function \( f(x) \) is negative at the immediate neighborhood of each root between two adjacent points.

3. **Determine Intervals:**
    - Analyze the sign of the function in each interval created by the critical points:
     - Check intervals: \( (-\infty, -3.5) \), \( (-3.5, 0.5) \), \( (0.5, 3) \), and \( (3, \infty) \).
    - Test a point in each interval to see if \( f(x) \) is positive or negative.
    
4. **Conclusion:**
    - The intervals where \( f(x) \) is positive will be the ranges between the critical points where the function value is greater than zero.

**Final Answer:**
\[ f(x) \text{ is positive on } \big((-\infty, -3.5) \cup (0.5, 3)\big). \]

**Note:**
This is a general step-by-step method; to fully confirm
Transcribed Image Text:--- ### Finding Intervals of Positivity for a Given Function **Problem Statement:** You are given the function: \[ f(x) = -2(x + 3.5)(x - 0.5)(x - 3) \] Your task is to find the intervals on which \( f(x) \) is positive by plotting a graph. #### Steps to Determine Intervals of Positivity: 1. **Identify Critical Points:** - Find the roots of the function where \( f(x) = 0 \). For the given function: \[ x + 3.5 = 0 \implies x = -3.5 \] \[ x - 0.5 = 0 \implies x = 0.5 \] \[ x - 3 = 0 \implies x = 3 \] The critical points are \( x = -3.5 \), \( x = 0.5 \), and \( x = 3 \). 2. **Plot the Graph:** - Sketch the polynomial function on a graph considering the critical points. - Determine where the function crosses the x-axis: at \( x = -3.5 \), \( x = 0.5 \), and \( x = 3 \). - The function \( f(x) \) is negative at the immediate neighborhood of each root between two adjacent points. 3. **Determine Intervals:** - Analyze the sign of the function in each interval created by the critical points: - Check intervals: \( (-\infty, -3.5) \), \( (-3.5, 0.5) \), \( (0.5, 3) \), and \( (3, \infty) \). - Test a point in each interval to see if \( f(x) \) is positive or negative. 4. **Conclusion:** - The intervals where \( f(x) \) is positive will be the ranges between the critical points where the function value is greater than zero. **Final Answer:** \[ f(x) \text{ is positive on } \big((-\infty, -3.5) \cup (0.5, 3)\big). \] **Note:** This is a general step-by-step method; to fully confirm
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