Find the common ratio for the sequence 3, negative 9 over 2, 27 over 4, negative 81 over 8, etc

Question

Find the common ratio for the sequence  

A
B
C
D	The sequence is not geometric, therefore there is no common ratio.

Answer 1

B: ratio = -3/2

It's an alternating sequence, so the common ratio has to be negative

That leaves only B or D.

3 x -3/2 = -9/2

-9/2 x -3/2 = 27/4

27/4 x -3/2 = -81/8

It works, it's a geometric sequence or progression

Answer 2

A geometric sequence has a constant common ratio. That means that (next term)/(current term) = constant.

So, (-9/2)/3 = (27/4)/(-9/2) = (-81/8)/(27/4) = . . .

Find the easy one: (-9/2)/3 = -3/2 and select B.