How do you write a rule for the nth term of the geometric sequence and then find a_5 given a_4=-3, r=-2?

1 Answer
Jim G.
Sep 10, 2017

a_n=3/8(-2)^(n-1),a_5=6

Explanation:

"the terms in a standard geometric sequence are"

a,ar,ar^2,ar^3, ...... , ar^(n-1)

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

"the nth term is "

•color(white)(x)a_n=ar^(n-1)

a_4=ar^3=-3rArra=(-3)/(-2)^3=(-3)/(-8)=3/8

rArra_n=3/8(-2)^(n-1)

rArra_5=3/8(-2)^4=3/8xx16=6

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