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ExamsJEE MainMaths

If 49^λ + 16ⁿ + λ is divisible by 64 for every n ∈ N, then the greatest negative value of λ is

  1. −2
  2. −1
  3. −3
  4. −4

Correct answer: −1

Solution

The expression 49^λ + 16ⁿ + λ must be evaluated under modulo 64 conditions. For n being a natural number, 16ⁿ is always divisible by 64 when n ≥ 2, thus the focus is on the terms 49^λ and λ. The term 49^λ can be simplified as (49 mod 64)^λ, which is 49, and we find that for λ = -1, the expression becomes 1 + 0, satisfying the divisibility condition. Hence, the greatest negative value of λ that maintains this divisibility is -1.

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