For what value of the number k is the following function continuous at r=2 if x < 2, if x = 2, if x > 2 f(x) = = (A) 3 (B) 2 (C) (D) All values of k work 1-x² k 3r-9 -3 (E) No such value of k exists

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...
Question
8
### Continuity of Piecewise Functions

For what value of the number \(k\) is the following function continuous at \(x = 2\)?

\[
f(x) = 
\begin{cases} 
1 - x^2 & \text{if } x < 2, \\
k & \text{if } x = 2, \\
3x - 9 & \text{if } x > 2 
\end{cases}
\]

**Options:**

- (A) 3
- (B) 2
- (C) -3
- (D) All values of \(k\) work
- (E) No such value of \(k\) exists

### Explanation:

To determine the value of \(k\) that makes the function continuous at \(x = 2\), we must ensure that:

\[
\lim_{{x \to 2^-}} f(x) = f(2) = \lim_{{x \to 2^+}} f(x)
\]

1. **Left-hand limit (\(\lim_{{x \to 2^-}} f(x)\))**:
    - When \(x < 2\), \(f(x) = 1 - x^2\).
    - \(\lim_{{x \to 2^-}} f(x) = 1 - 2^2 = 1 - 4 = -3\).

2. **Right-hand limit (\(\lim_{{x \to 2^+}} f(x)\))**:
    - When \(x > 2\), \(f(x) = 3x - 9\).
    - \(\lim_{{x \to 2^+}} f(x) = 3(2) - 9 = 6 - 9 = -3\).

3. **Value of the function at \(x = 2\), \(f(2)\)**:
    - This is given as \(k\).

### Conclusion:
For the function to be continuous at \(x = 2\):

\[
\lim_{{x \to 2^-}} f(x) = f(2) = \lim_{{x \to 2^+}} f(x)
\]

\[
-3 = k = -3
\]

Hence, the value of \(k\) must be
Transcribed Image Text:### Continuity of Piecewise Functions For what value of the number \(k\) is the following function continuous at \(x = 2\)? \[ f(x) = \begin{cases} 1 - x^2 & \text{if } x < 2, \\ k & \text{if } x = 2, \\ 3x - 9 & \text{if } x > 2 \end{cases} \] **Options:** - (A) 3 - (B) 2 - (C) -3 - (D) All values of \(k\) work - (E) No such value of \(k\) exists ### Explanation: To determine the value of \(k\) that makes the function continuous at \(x = 2\), we must ensure that: \[ \lim_{{x \to 2^-}} f(x) = f(2) = \lim_{{x \to 2^+}} f(x) \] 1. **Left-hand limit (\(\lim_{{x \to 2^-}} f(x)\))**: - When \(x < 2\), \(f(x) = 1 - x^2\). - \(\lim_{{x \to 2^-}} f(x) = 1 - 2^2 = 1 - 4 = -3\). 2. **Right-hand limit (\(\lim_{{x \to 2^+}} f(x)\))**: - When \(x > 2\), \(f(x) = 3x - 9\). - \(\lim_{{x \to 2^+}} f(x) = 3(2) - 9 = 6 - 9 = -3\). 3. **Value of the function at \(x = 2\), \(f(2)\)**: - This is given as \(k\). ### Conclusion: For the function to be continuous at \(x = 2\): \[ \lim_{{x \to 2^-}} f(x) = f(2) = \lim_{{x \to 2^+}} f(x) \] \[ -3 = k = -3 \] Hence, the value of \(k\) must be
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