Q44 / 160 · AP EAMCET 2021 (19 Aug Shift 2) · Mathematics

For what natural numbers n∈N, the inequality 2n>n+1 is valid?

  • A
    ∀n∈N
  • Correct answer
    B
    ∀n≥2
  • C
    ∀1≤n≤3
  • D
    ∀n∈N−{2,3}

Solution

Given that, 2n>n+1

For n=1, 21>1+1⇒2>2 is not true

For n=2, 22>2+1⇒4>3 is True.

So, Given inequality is true for n=2.

Assume that  2m>m+1 is true for m>2.

But 2m>1 for all m>1

⇒2m+2m>m+1+1

⇒2m+1>m+1+1

Hence, the inequality holds for n=m+1

It follows by mathematical induction that the given inequality holds for all natural numbers n≥2.

Hence, the correct answer is option: 'B'.

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