Answer:
Common ratio is -1/2
Explanation:
Common ratio is the amount between each number in a geometric sequence.
It is called the common ratio because it is the same to each number.
Common ratio is the ratio between two successive numbers in a geometric sequence.
Common is a gotten by either division or multiplication.
Therefore in the case above
1/2 x -1/2 = -1/4 ......
-1/4 x -1/2 = 1/8 ......
1/8 x -1/2 = -1/16 ....etc
Therefore our common ratio is -1/2