Answer
The given sequence is a geometric sequence because the ratio of any two consecutive terms is constant.
The common ratio = -3
Work Step by Step
The given sequence is = 1, -3, 9, -27, 81,......
This is a geometric sequence because the ratio of any two consecutive terms is constant.
The common ratio = $\frac{81}{-27}$ = $\frac{-27}{9}$ = $\frac{9}{-3}$ = $\frac{-3}{1}$ = -3