Question

Which of the following is the formula for the geometric sequence?
8, -16, 32, -64,...
A a=8(-2)^n-1
B a=2(-8)^n-1
C a=-8(2^n-1)

Answer 1

The best way to do this problem is to plug in numbers for n. When you let n=1, you should get 8. When you let n=2, you should get -16.

Answer 2

For example, let n=1. For equation A, you get
\[a_1=8(-2)^{1-1}=8\]which is correct. However, for equation B, you get
\[a_1=2(-8)^{1-1}=2\]which is wrong, because you were supposed to get 8. Therefore, you know Equation B is wrong.

Answer 3

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