How do you write a rule for the nth term of the geometric sequence and then find a_5 given a_3=-144, r=0.5?

1 Answer
Jim G.
Dec 15, 2017

a_n=-576(0.5)^(n-1),a_5=-36

Explanation:

"the nth term of a geometric sequence is "

•color(white)(x)a_n=ar^(n-1)

"where a is the first term and r the common ratio"

a_3=ar^2=-144

rArra=-144/(0.25)=-576larrcolor(blue)"first term"

rArra_n=-576(0.5)^(n-1)

rArra_5=-576xx(0.5)^4=-36

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