I need help!!!

3/2,1/2, 1/6,1/8,...
I need to determine if this sequence is arithmetic, geometric, or neither, then I need to find the ninth term

is (1/2) - (3/2) = (1/6)-(1/2)

if yes, then arithmetic, but it isn't.

is (1/2) ÷ (3/2) = (1/6)÷(1/2)
if yes, then geometric
1/2 ÷ 3/2 = 1/3
(1/6)÷(1/2) = 1/3
but
(1/8) ÷ (1/6) = .75 (no good)

so the sequence is neither arithmetic nor geometric.