One–Sided Limits — Question 2

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Question 2

Let the function ff be defined as follows: f(x)={3x+1,x<1x2,x≥1f(x) = \begin{cases} 3x + 1, & x < 1 \\ x^2, & x \geq 1 \end{cases}

(a) Compute lim⁡x→1−f(x)\lim_{x \to 1^-} f(x)

(b) Compute lim⁡x→1+f(x)\lim_{x \to 1^+} f(x)

(c) Does lim⁡x→1f(x)\lim_{x \to 1} f(x) exist? Justify your answer.

Original worksheet page 1: question and worked solution for 2-3-002
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Question 2 - Solution

We are given: f(x)={3x+1,x<1x2,x≥1f(x) = \begin{cases} 3x + 1, & x < 1 \\ x^2, & x \geq 1 \end{cases}

(a) Left-hand limit: For x<1x < 1, use f(x)=3x+1f(x) = 3x + 1: limx→1−f(x)=limx→1−(3x+1)=3(1)+1=4\lim_{x \to 1^-} f(x) = \lim_{x \to 1^-} (3x + 1) = 3(1) + 1 = 4

(b) Right-hand limit: For x≥1x \geq 1, use f(x)=x2f(x) = x^2: limx→1+f(x)=limx→1+x2=12=1\lim_{x \to 1^+} f(x) = \lim_{x \to 1^+} x^2 = 1^2 = 1

(c) Two-sided limit: Since the left and right limits are not equal: limx→1−f(x)=4andlimx→1+f(x)=1⇒limx→1f(x) does not exist\lim_{x \to 1^-} f(x) = 4 \quad \text{and} \quad \lim_{x \to 1^+} f(x) = 1 \Rightarrow \lim_{x \to 1} f(x) \text{ does not exist}

Final Answer: limx→1−f(x)=4,limx→1+f(x)=1,limx→1f(x) does not exist\boxed{ \lim_{x \to 1^-} f(x) = 4, \quad \lim_{x \to 1^+} f(x) = 1, \quad \lim_{x \to 1} f(x) \text{ does not exist} }

Original worksheet page 2: question and worked solution for 2-3-002

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