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Classify the discontinuity of r(x) at x = 2

Consider the function r(x)=x3−8x−2r(x) = \dfrac{x^3 - 8}{x - 2} which is undefined at x=2x = 2.

The function r(x)=x3−8x−2r(x) = \dfrac{x^3 - 8}{x-2} is not defined at x=2x = 2. Determine whether lim⁡x→2r(x)\lim_{x\to 2} r(x) exists, and use this to classify the discontinuity at x=2x=2 as removable, jump, or infinite. If the discontinuity is removable, state the value that r(x)r(x) would need to be assigned at x=2x=2 in order to make it continuous there.

Hint

Factor the numerator as a difference of cubes: x3−8=(x−2)(x2+2x+4)x^3 - 8 = (x-2)(x^2+2x+4), then simplify the fraction before taking the limit.

Step-by-step solution

Factor the numerator using the difference of cubes formula: x3−8=(x−2)(x2+2x+4)x^3 - 8 = (x-2)(x^2+2x+4). For x≠2x \neq 2, this lets us cancel the common factor of (x−2)(x-2), giving r(x)=x2+2x+4r(x) = x^2 + 2x + 4 whenever x≠2x \neq 2.

Since r(x)r(x) agrees with the polynomial x2+2x+4x^2+2x+4 for all xx near but not equal to 22, the limit as x→2x\to 2 exists and equals 22+2(2)+4=122^2+2(2)+4 = 12. Because r(2)r(2) is undefined but the limit exists (and is finite), this is a removable discontinuity — the graph has a hole at (2,12)(2,12) that could be patched by defining r(2)=12r(2)=12.

Feature of the graph at the removable discontinuity

Hint
Step-by-step solution

The graph shows a hole. Since the discontinuity at x equals two is removable, the limit exists and equals twelve, but the function value there is undefined. This creates a single missing point on an otherwise continuous curve, which is visually represented as a hole rather than a jump or a break from an asymptote.

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