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One-sided and two-sided limit of a piecewise function at a boundary point

Consider the piecewise function w(x)={2x+1x<2x2x≥2w(x) = \begin{cases} 2x+1 & x < 2 \\ x^2 & x \ge 2 \end{cases}

Using the limit laws, evaluate lim⁡x→2−w(x)\lim_{x \to 2^-} w(x) and lim⁡x→2+w(x)\lim_{x \to 2^+} w(x). Based on these two one-sided limits, determine whether lim⁡x→2w(x)\lim_{x \to 2} w(x) exists, and if it does, find its value.

Hint

For xx near 22 but less than 22, use the formula 2x+12x+1 and apply direct substitution with the sum and product rules. For xx near 22 but greater than or equal to 22, use x2x^2 and apply the power rule. Compare the two results.

Step-by-step solution

For x<2x < 2, w(x)=2x+1w(x) = 2x+1, which is a polynomial and hence continuous, so by direct substitution and the sum and product rules, lim⁡x→2−w(x)=2(2)+1=5\lim_{x \to 2^-} w(x) = 2(2)+1 = 5.

For x≥2x \ge 2, w(x)=x2w(x) = x^2, and by the power rule, lim⁡x→2+w(x)=22=4\lim_{x \to 2^+} w(x) = 2^2 = 4. Since the left-hand limit (5) and right-hand limit (4) are not equal, the two-sided limit lim⁡x→2w(x)\lim_{x \to 2} w(x) does not exist.

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