MCQ
$n^2 < 2^n$ for all natural numbers:
  • $n ≥ 5$
  • B
    $n < 5$
  • C
    $n > 1$
  • D
    $n ≤ 3$

Answer

Correct option: A.
$n ≥ 5$
Consider, $P(n) : n^2 < 2^n$
Substituting $n = 1, 2, 3,…$
$P(1): 1^2< 2^1$
$1 < 2 ($not true$)$
$P(2): 2^2 < 2^2$
$4 < 4 ($not true$)$
$P(3): 3^2 < 2^3$
$9 < 8 ($not true$)$
$P(4): 4^2 < 2^4$
$16 < 16 ($not true$)$
$P(5): 5^2 < 2^5$
$25 < 32 ($true$)$
$P(6): 6^2 < 2^6$
$26 < 64 ($true$)$
Thus, $n^2 < 2^n$ for all natural numbers $n ≥ 5.$

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