Detemine where the given function is increasing and where it is decreasing. s(x) = -x 2 - 14x - 40 O Decreasing on (-~. -7), increasing on (-7, ) O Increasing on (-*, *) Decreasing on (-*, -7) and (0, *), increasing on (-7, 0) Increasing on (-*, -7), decreasing on (-7, *)
Detemine where the given function is increasing and where it is decreasing. s(x) = -x 2 - 14x - 40 O Decreasing on (-~. -7), increasing on (-7, ) O Increasing on (-*, *) Decreasing on (-*, -7) and (0, *), increasing on (-7, 0) Increasing on (-*, -7), decreasing on (-7, *)
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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![### Determine Where the Given Function is Increasing and Where It is Decreasing
Given the function:
\[ s(x) = -x^2 - 14x - 40 \]
Select the correct intervals where the function is either increasing or decreasing from the following options:
1. Decreasing on \((-\infty, -7)\), increasing on \((-7, \infty)\)
2. Increasing on \((-\infty, \infty)\)
3. Decreasing on \((-\infty, -7)\) and \((0, \infty)\), increasing on \((-7, 0)\)
4. Increasing on \((-\infty, -7)\), decreasing on \((-7, \infty)\)
### Explanation
To determine the intervals of increase and decrease, find the critical points by first taking the derivative of the function \(s(x)\):
\[ s'(x) = \frac{d}{dx}(-x^2 - 14x - 40) = -2x - 14 \]
Set the derivative equal to zero to find the critical points:
\[ -2x - 14 = 0 \]
\[ -2x = 14 \]
\[ x = -7 \]
Now, test the intervals divided by the critical point \(x = -7\) to determine where the function is increasing and decreasing. The intervals to test are \((-\infty, -7)\) and \((-7, \infty)\):
- For \(x \in (-\infty, -7)\): Choose a test point like \(x = -8\).
\[ s'(-8) = -2(-8) - 14 = 16 - 14 = 2 \]
(Note: If the derivative is positive, the function is increasing.)
- For \(x \in (-7, \infty)\): Choose a test point like \(x = 0\).
\[ s'(0) = -2(0) - 14 = -14 \]
(Note: If the derivative is negative, the function is decreasing.)
Thus, \(s(x)\) is decreasing on \((-\infty, -7)\) and increasing on \((-7, \infty)\).
Based on this analysis, the correct choice is:
***Decreasing on \((-\infty, -7)\), increasing on \((-7, \infty)\](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F670cec44-172f-4f6c-8b5b-add8e60675be%2Fff231b4e-8876-4019-9a97-ec486a33a17d%2Fbyrz4hb.png&w=3840&q=75)
Transcribed Image Text:### Determine Where the Given Function is Increasing and Where It is Decreasing
Given the function:
\[ s(x) = -x^2 - 14x - 40 \]
Select the correct intervals where the function is either increasing or decreasing from the following options:
1. Decreasing on \((-\infty, -7)\), increasing on \((-7, \infty)\)
2. Increasing on \((-\infty, \infty)\)
3. Decreasing on \((-\infty, -7)\) and \((0, \infty)\), increasing on \((-7, 0)\)
4. Increasing on \((-\infty, -7)\), decreasing on \((-7, \infty)\)
### Explanation
To determine the intervals of increase and decrease, find the critical points by first taking the derivative of the function \(s(x)\):
\[ s'(x) = \frac{d}{dx}(-x^2 - 14x - 40) = -2x - 14 \]
Set the derivative equal to zero to find the critical points:
\[ -2x - 14 = 0 \]
\[ -2x = 14 \]
\[ x = -7 \]
Now, test the intervals divided by the critical point \(x = -7\) to determine where the function is increasing and decreasing. The intervals to test are \((-\infty, -7)\) and \((-7, \infty)\):
- For \(x \in (-\infty, -7)\): Choose a test point like \(x = -8\).
\[ s'(-8) = -2(-8) - 14 = 16 - 14 = 2 \]
(Note: If the derivative is positive, the function is increasing.)
- For \(x \in (-7, \infty)\): Choose a test point like \(x = 0\).
\[ s'(0) = -2(0) - 14 = -14 \]
(Note: If the derivative is negative, the function is decreasing.)
Thus, \(s(x)\) is decreasing on \((-\infty, -7)\) and increasing on \((-7, \infty)\).
Based on this analysis, the correct choice is:
***Decreasing on \((-\infty, -7)\), increasing on \((-7, \infty)\
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