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

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

Step-by-step 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)