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EXERCISE 4.1 · Q1

Q.Prove by method of induction, for all n∈Nn \in N: 2+4+6+…+2n=n(n+1)2 + 4 + 6 + \ldots + 2n = n(n+1).

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✓ Free question

Let P(n):2+4+⋯+2n=n(n+1)P(n):2+4+\cdots+2n=n(n+1). Base case (n=1n=1): L.H.S.=2=2, R.H.S.=1(2)=2=1(2)=2; equal, so P(1)P(1) holds. Inductive hypothesis: assume P(k)P(k): 2+4+⋯+2k=k(k+1)2+4+\cdots+2k=k(k+1). Inductive step: add 2(k+1)2(k+1) to both sides: 2+4+⋯+2k+2(k+1)=k(k+1)+2(k+1)=(k+1)(k+2)2+4+\cdots+2k+2(k+1)=k(k+1)+2(k+1)=(k+1)(k+2), which is exactly P(k+1)P(k+1). Conclusion: by the Principle of Mathematical Induction, P(n)P(n) holds for every n∈Nn\in N.

✓Final answer

2+4+6+⋯+2n=n(n+1)2+4+6+\cdots+2n=n(n+1), proved for all n∈Nn\in N.

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