How do you write a rule for the nth term of the geometric sequence and then find $a_5$ given $a_1=17, r=-2$ ?

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Answer 1 · 2017-03-15T13:41:00

$a_5=272.$

In the Usual Notation for Geo. Seq.,

$a_n=a_1*r^(n-1), n in NN.$

With, $a_1=17, and, r=-2,$ we have,

$a_n=17(-2)^(n-1), n in NN.$

Accordingly, $a_5=17(-2)^(5-1)=(17)(16)=272.$

How do you write a rule for the nth term of the geometric sequence and then find a_5a_5 given a_1=17, r=-2a_1=17, r=-2?