Question

For the following geometric sequence, find the explicit formula.
{1.-3,9 ...}

Answer 1

an = (-3)^(n-1).

Explanation:

The formula for the nth term an = a1r^(n-1) where a1 = first term and r = the common ratio.

In our series a1 = 1 and r = -3/1 = -3 so the explicit formula is:

1. * (-3)^(n-1)