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Classify the discontinuity at x = 2

Consider the function w(x)=x2−5x+6x2−4w(x) = \dfrac{x^2 - 5x + 6}{x^2 - 4}.

The function w(x)=x2−5x+6x2−4w(x) = \dfrac{x^2 - 5x + 6}{x^2 - 4} is discontinuous at x=2x = 2. Determine whether this discontinuity is removable, a jump discontinuity, or an infinite discontinuity. Justify your classification by factoring the numerator and denominator and examining what happens to w(x)w(x) near x=2x = 2.

Hint

Factor both the numerator and denominator completely, then see if a common factor cancels. If a factor cancels, check whether the limit as x→2x \to 2 exists and is finite, even though w(2)w(2) itself is undefined.

Step-by-step solution

Factor both the numerator and denominator: x2−5x+6=(x−2)(x−3)x^2 - 5x + 6 = (x-2)(x-3) and x2−4=(x−2)(x+2)x^2 - 4 = (x-2)(x+2). So w(x)=(x−2)(x−3)(x−2)(x+2)w(x) = \dfrac{(x-2)(x-3)}{(x-2)(x+2)}. Since x=2x = 2 makes both factors zero, w(2)w(2) is undefined (0/0 form), but the factor (x−2)(x-2) cancels for x≠2x \neq 2.

For x≠2x \neq 2, w(x)=x−3x+2w(x) = \dfrac{x-3}{x+2}, so lim⁡x→2w(x)=2−32+2=−14\lim_{x\to 2} w(x) = \dfrac{2-3}{2+2} = -\dfrac{1}{4}. This limit exists and is finite, but f(2)f(2) is undefined, so the second and third conditions of continuity fail while the limit itself exists. This means the graph has a hole at (2,−1/4)(2, -1/4) that could be patched by defining w(2)=−1/4w(2) = -1/4.

Classify the discontinuity at x = 2 — solution graph

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