Find the nth term An of the geometric sequence described below where r is the common ratio. Kind of confused on what to do?

Question

A4= -8
R= -2

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Answer 1 · 2017-10-12T19:34:12

# (-2)^(n-1), n in NN.#

We are given the fourth term #A_4,# and the common ratio #R# of a GP.

We have to find the #n^(th)" term "A_n# of the GP.

Recall that, #A_n=A_1*R^(n-1), n in NN.#

#:. A_4=-8, R=-2 rArr A_1*(-2)^(4-1)=-8.#

#:. A_1*(-8)=-8 :. A_1=1.#

#:. A_n=A_1*R^(n-1)=1*(-2)^(n-1)=(-2)^(n-1), n in NN.#