Limit with Difference of Cubes

When evaluating a limit like x3−a3x−a\frac{x^3 - a^3}{x - a}, use the difference of cubes identity:

x3−a3=(x−a)(x2+ax+a2)x^3 - a^3 = (x - a)(x^2 + ax + a^2)

Example:

limx→2x3−8x−2\lim_{x \to 2} \frac{x^3 - 8}{x - 2}
  1. Recognize $8 = 2^3$
  2. Apply identity:
(x−2)(x2+2x+4)x−2\frac{(x - 2)(x^2 + 2x + 4)}{x - 2}
  1. Cancel x−2x - 2
  2. Evaluate at x=2x = 2: $4 + 4 + 4 = 12$

This method avoids undefined division and simplifies the expression cleanly.

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