Logan Bates
10/10/2023 · Primary School
Let \( f(x)=\left\{\begin{array}{ll}2 x+9 & \text { if } x<-3 \\ \sqrt{x+12} & \text { if } x>-3 \\ 2 & \text { if } x=-3\end{array}\right. \) Select all statements below that you agree with. Note: You may be checking more than one box. No partial credit. \( \square f(-3) \) is defined. \( \lim _{x \rightarrow-3} f(x) \) exists. \( \lim _{x \rightarrow-3} f(x)=f(-3) \). \( \square \) The function is continuous at \( x=-3 \). \( \square \) The function is not continuous at \( x=-3 \).
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Tutor-Verified Answer
Step-by-step Solution
Let's analyze the function \( f(x) \) and the statements provided.
1. **Check if \( f(-3) \) is defined:**
\[
f(-3) = 2 \quad \text{(since the definition states that if } x = -3, f(x) = 2\text{)}
\]
Therefore, \( f(-3) \) is defined.
2. **Check if \( \lim_{x \rightarrow -3} f(x) \) exists:**
We need to find the left-hand limit and the right-hand limit as \( x \) approaches \(-3\).
- **Left-hand limit** (\( x \to -3^- \)):
\[
f(x) = 2x + 9 \quad \text{for } x < -3
\]
\[
\lim_{x \to -3^-} f(x) = 2(-3) + 9 = -6 + 9 = 3
\]
- **Right-hand limit** (\( x \to -3^+ \)):
\[
f(x) = \sqrt{x + 12} \quad \text{for } x > -3
\]
\[
\lim_{x \to -3^+} f(x) = \sqrt{-3 + 12} = \sqrt{9} = 3
\]
Since both the left-hand limit and right-hand limit are equal:
\[
\lim_{x \to -3} f(x) = 3
\]
Thus, \( \lim_{x \rightarrow -3} f(x) \) exists.
3. **Check if \( \lim_{x \rightarrow -3} f(x) = f(-3) \):**
We found that:
\[
\lim_{x \to -3} f(x) = 3 \quad \text{and} \quad f(-3) = 2
\]
Since \( 3 \neq 2 \), we have:
\[
\lim_{x \rightarrow -3} f(x) \neq f(-3)
\]
4. **Check if the function is continuous at \( x = -3 \):**
A function is continuous at a point if:
\[
\lim_{x \to c} f(x) = f(c)
\]
Since we found that \( \lim_{x \to -3} f(x) = 3 \) and \( f(-3) = 2 \), the function is not continuous at \( x = -3 \).
Now, let's summarize the statements:
- \( \square f(-3) \) is defined. **(True)**
- \( \lim_{x \rightarrow -3} f(x) \) exists. **(True)**
- \( \lim_{x \rightarrow -3} f(x) = f(-3) \). **(False)**
- \( \square \) The function is continuous at \( x = -3 \). **(False)**
- \( \square \) The function is not continuous at \( x = -3 \). **(True)**
Thus, the correct selections are:
- \( \square f(-3) \) is defined.
- \( \lim_{x \rightarrow -3} f(x) \) exists.
- \( \square \) The function is not continuous at \( x = -3 \).
Quick Answer
f(-3) is defined, the limit exists, and the function is not continuous at x = -3.
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