Use the formula to evaluate the series - 3+6-12+24 - ... - a7

If the question is asking for a7, the answer is - 192.

The common ratio, r, is found by dividing from right to left.

24/-12 = - 2

-12/6 = - 2

r = - 2

To continue the series multiply by - 2.

24*-2 = - 48

-48*-2=96

96*-2=-192