# Chapter 11 - Section 11.1 - Sequences and Summation Notation - Exercise Set - Page 829: 16

$-2-2,-4,-12$

#### Work Step by Step

Need to find the first four terms of $a_n=-2(n-1)!$ when $n=1,2,3,4$ Thus, $a_1=-2(1-1)!=-2$ $a_2=-2(2-1)!=-2(1)=-2$ $a_3=-2(3-1)!=-2(2.1)=-4$ $a_4=-2(4-1)!=-2(3.2.1)=-12$ Hence, the first four terms are: $-2-2,-4,-12$

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