Skip to content
EXERCISE 4.1 · Q12

Q.Prove by method of induction, for all n∈Nn \in N: 3n−2n−13^n - 2n - 1 is divisible by 44.

Maharashtra MsbshseTextbookSubjectiveImportance★★★★★est
9% · 12/129 Questions
🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

Let P(n):3n−2n−1=4mP(n):3^n-2n-1=4m. Base: n=1n=1: 3−2−1=0=4(0)3-2-1=0=4(0); divisible by 4 (0 counts as a multiple), so holds. Hypothesis: assume 3k−2k−1=4a3^k-2k-1=4a, i.e. 3k=4a+2k+13^k=4a+2k+1. Step: 3k+1−2(k+1)−1=3⋅3k−2k−3=3(4a+2k+1)−2k−3=12a+6k+3−2k−3=12a+4k=4(3a+k)3^{k+1}-2(k+1)-1=3\cdot3^k-2k-3=3(4a+2k+1)-2k-3=12a+6k+3-2k-3=12a+4k=4(3a+k), a mu …

Unlock everything free for 14 days

  • Full step-by-step solutions
  • Concept-first explanations
  • Methods, shortcuts & mistakes
  • PYQ mapping + timed mock tests

Full access for 14 days. No credit card required.