Question

Which of the following choices is the explicit formula for the following geometric sequence?

-0.1, 0.04, -0.016, 0.0064, -0.00256, ...

A. an = -0.1(-0.4)n-1
B. an = 0.4(-0.4)n-1
C. an = 0.1(-0.4)n-1
D. an = 0.1(0.4)n
E. an = -0.1(0.4)n-1

Answer 1

an = a r^(n-1)

where a = first term and r = common ration

r can be found by dividing the second term by the first

Answer 2

* common ratio

Answer 3

here a = -0.1 and r = 0.04 / -0.1