Carter Sullivan
07/05/2024 · High School
Consider the following function. \[ f(x)=\left\{\begin{array}{lll}x^{2}+x & \text { if } \quad x<-3 \\ 6 & \text { if } & x=-3 \\ 2 x-1 & \text { if } & x>-3\end{array}\right. \] Evaluate the given limits. If a limit does not exist, enter DNE. (a) \( \lim _{x \rightarrow-3^{-}} f(x)=\square \) (b) \( \lim _{x \rightarrow-3^{+}} f(x)=\square \) (c) \( \lim _{x \rightarrow-3} f(x)=\square \)
UpStudy ThothAI Solution
Tutor-Verified Answer
Step-by-step Solution
To evaluate the limits for the given piecewise function \( f(x) \), we will analyze the function as \( x \) approaches \(-3\) from the left and from the right.
### (a) \( \lim _{x \rightarrow-3^{-}} f(x) \)
For \( x < -3 \), the function is defined as:
\[
f(x) = x^2 + x
\]
We will calculate the limit as \( x \) approaches \(-3\) from the left:
\[
\lim_{x \to -3^{-}} f(x) = \lim_{x \to -3^{-}} (x^2 + x)
\]
Substituting \( x = -3 \):
\[
= (-3)^2 + (-3) = 9 - 3 = 6
\]
Thus,
\[
\lim _{x \rightarrow-3^{-}} f(x) = 6
\]
### (b) \( \lim _{x \rightarrow-3^{+}} f(x) \)
For \( x > -3 \), the function is defined as:
\[
f(x) = 2x - 1
\]
We will calculate the limit as \( x \) approaches \(-3\) from the right:
\[
\lim_{x \to -3^{+}} f(x) = \lim_{x \to -3^{+}} (2x - 1)
\]
Substituting \( x = -3 \):
\[
= 2(-3) - 1 = -6 - 1 = -7
\]
Thus,
\[
\lim _{x \rightarrow-3^{+}} f(x) = -7
\]
### (c) \( \lim _{x \rightarrow-3} f(x) \)
The limit as \( x \) approaches \(-3\) exists only if the left-hand limit and the right-hand limit are equal. We found:
\[
\lim _{x \rightarrow-3^{-}} f(x) = 6
\]
\[
\lim _{x \rightarrow-3^{+}} f(x) = -7
\]
Since these two limits are not equal, the overall limit does not exist:
\[
\lim _{x \rightarrow-3} f(x) = \text{DNE}
\]
### Final Answers:
(a) \( \lim _{x \rightarrow-3^{-}} f(x) = 6 \)
(b) \( \lim _{x \rightarrow-3^{+}} f(x) = -7 \)
(c) \( \lim _{x \rightarrow-3} f(x) = \text{DNE} \)
Quick Answer
(a) \( \lim _{x \rightarrow-3^{-}} f(x) = 6 \)
(b) \( \lim _{x \rightarrow-3^{+}} f(x) = -7 \)
(c) \( \lim _{x \rightarrow-3} f(x) = \text{DNE} \)
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