Find the limit L = limx→1 (x4 − 1)/(x − 1).
Find L
Show hints
- Substitution gives 0/0. Factor the numerator.
- xⁿ − aⁿ = (x − a)(xⁿ⁻¹ + a·xⁿ⁻² + … + aⁿ⁻¹).
- x4 − 1 = (x − 1)(x3 + x2 + x + 1).
Show the answer and the step-by-step solution
Limits: first try direct substitution. If it gives 0/0, simplify first: factor and cancel the common factor, or multiply by the conjugate. As x → ∞, divide numerator and denominator by the highest power of x. L'Hôpital's rule: if f/g gives 0/0 or ∞/∞, then lim f/g = lim f′/g′, differentiating the numerator and the denominator separately (not with the quotient rule).
Try direct substitution
Factor and cancel
Substitute
Answer
This is the derivative of xⁿ at x = a: n·aⁿ⁻¹.