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JEE Main201910 Apr 2019Morning ShiftMathematicsLimitsActual

If l i m x → 1 x 4 - 1 x - 1 = l i m x → k x 3 - k 3 x 2 - k 2 , then k is

Options

  1. A3 2
  2. B4 3
  3. C3 8
  4. D8 3

Correct answer

D. 8 3

Step-by-step solution

Given limits can be written as, l i m x → 1 x 2 + 1 x + 1 x - 1 x - 1 = l i m x → k x - k x 2 + k 2 + x k x - k x + k ⇒ 4 = 3 k 2 2 k ⇒ k = 8 3 .

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