Math, asked by Swarup1998, 1 year ago

Use the principle of induction to prove that

1.1! + 2.2! + ... + n.n! = (n+1)! - 1

for all n \in \mathbb{N}.

Answers

Answered by piyushkumar22
12


Let P(k) be the statement that: 
1.1! + 2.2! + ... + k.k! = (k+1)! -1, where k is a positive integer. 

For k = 1, as 1! = 2! - 1, P(1) is obviously true. 

Now suppose that P(n) is true. 
Then 1.1! + 2.2! + ... + n.n! = (n+1)! -1. 

Adding (n+1).(n+1)! to both sides, we have: 
1.1! + 2.2! + ... + n.n! + (n+1)(n+1)! 
= (n+1)! - 1 + (n+1)(n+1)! 
= (n+1)! + (n+1)(n+1)! - 1 
= (n+1)!{1 + (n+1)} - 1 
= (n+2)! - 1 

It follows that P(n+1) is true. Therefore, by induction, P(k) is true for all positive integer k. 

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Answered by generalRd
6

plz refer to the attachment for answer

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