## Precalculus (6th Edition) Blitzer

First five terms $5,-15,45,-135,405$
Given: $a_1=5$ and $r=-3$ Formula for a Geometric sequence, so $a_n=5(-3)^{n-1}$ when n=2; $a_2=a_1r=5(-3)=-15$ when n=3 ; $a_3=a_2r=-15(-3)=45$ when n=4 ;$a_4=a_3r=45(-3)=-135$ when n= 5;$a_5=a_4r=-135(-3)=405$ Thus, First five terms $5,-15,45,-135,405$