Verified answer

A geometric sequence is a set of numbers where the next number is multiplied by a set constant. In this case, we divide a4 by a3 to find the multiplying factor and we find it to be -2/3. To find a1, we must divide a3 by the factor twice, once to get to a2 and once to get a1:

a2 = a3/(-2/3) = 72

a1 = a2/(-2/3) = -108

If these are the only two "points" you have to work with, a1 can be worked out logically: (1) the difference between a3 & a4 is 80 (2) a2 would be -128 and (3) a1 would be -208

a4 = 32

a3 = -48

a2 = 72

a1 = -108

but I think I can think of others?????????