Question

Which of the following choices is the explicit formula for the following geometric sequence? -0.1, 0.02, -0.004, 0.0008, -0.000016

Answer 1

The rule for a geometric sequence is:

a(n)=ar^(n-1) so we can use two points to find the common ratio...

0.02/-.1=ar/ar^0

-0.2=r, so the common ratio is -0.2 and the first term is -0.1 so

a(n)=-0.1(-0.2^(n-1))