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MISCELLANEOUS EXERCISE 4 (II) · Q96

Q.Prove, by method of induction, for all n∈Nn \in N: 2+3.2+4.22+…+(n+1)2n−1=n.2n2 + 3.2 + 4.2^2 + \ldots + (n+1)2^{n-1} = n. 2^n.

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✓ Free question

Let P(n):2+3.2+4.22+⋯+(n+1)2n−1=n.2nP(n):2+3.2+4.2^2+\cdots+(n+1)2^{n-1}=n.2^n. Base: n=1n=1: L.H.S.=2=2, R.H.S.=1(2)=2=1(2)=2; holds. Hypothesis: assume true for kk: sum=k.2k=k.2^k. Step: add (k+2)2k(k+2)2^k: k.2k+(k+2)2k=(2k+2)2k=2(k+1)2k=(k+1)2k+1k.2^k+(k+2)2^k=(2k+2)2^k=2(k+1)2^k=(k+1)2^{k+1}, matching the target n.2nn.2^n at n=k+1n=k+1. Conclusion: true for all n∈Nn\in N.

✓Final answer

2+3.2+4.22+⋯+(n+1)2n−1=n.2n2+3.2+4.2^2+\cdots+(n+1)2^{n-1}=n.2^n, proved for all n∈Nn\in N.

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