Common Graphs — Question 8

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Question 8

Sketch the graph of the piecewise function: f(x)={x+2if x<−1x2if −1≤x≤24−xif x>2f(x) = \begin{cases} x + 2 & \text{if } x < -1 \\ x^2 & \text{if } -1 \le x \le 2 \\ 4 - x & \text{if } x > 2 \end{cases}

Instructions: Clearly indicate open and closed points on the graph. Identify points of discontinuity, if any.

Original worksheet page 1: question and worked solution for 1-10-008
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Question 8 - Solution

We are given a piecewise function: f(x)={x+2if x<−1x2if −1≤x≤24−xif x>2f(x) = \begin{cases} x + 2 & \text{if } x < -1 \\ x^2 & \text{if } -1 \le x \le 2 \\ 4 - x & \text{if } x > 2 \end{cases}

Step 1: Evaluate endpoints to check continuity.

From the left of x=−1x = -1, lim⁡x→−1−f(x)=−1+2=1\lim_{x \to -1^-} f(x) = -1 + 2 = 1

At x=−1x = -1, f(−1)=(−1)2=1⇒continuousf(-1) = (-1)^2 = 1 \Rightarrow \text{continuous}

From the right of x=2x = 2, lim⁡x→2+f(x)=4−2=2\lim_{x \to 2^+} f(x) = 4 - 2 = 2

At x=2x = 2, f(2)=22=4⇒discontinuous at x=2f(2) = 2^2 = 4 \Rightarrow \text{discontinuous at } x = 2

Discontinuity: Jump discontinuity at x=2x = 2

See the diagram in the original worksheet below.

Original worksheet page 2: question and worked solution for 1-10-008

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