MathCastle
Proof Writing & Problem SolvingEasy

Proof Writing & Problem Solving · Easy problem

Induction proves 1⋅1!+2⋅2!+⋯+n⋅n!=(n+1)!−11 \cdot 1! + 2 \cdot 2! + \cdots + n \cdot n! = (n+1)! - 1; the step uses (k+1)!−1+(k+1)(k+1)!=(k+2)!−1(k+1)! - 1 + (k+1)(k+1)! = (k+2)! - 1. What is 1⋅1!+2⋅2!+3⋅3!+4⋅4!+5⋅5!1 \cdot 1! + 2 \cdot 2! + 3 \cdot 3! + 4 \cdot 4! + 5 \cdot 5!?

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