Which function forms a geometric sequence when x = 1, 2, 3, f(x)=8x-9 f(x)=-2(3/4)x f(x)=2/3x5 f(x)=6-4/x

The geometric sequence is found in the relationship between consecutive terms that is constant.
 In this problem, as I understand it, none of the functions forms a geometric sequence.
 The functions that form a geometric sequence have the form
 f (x) = h (a) ^ n where "a" is the constant relation between the successive terms.
 If you wrote the function "f (x) = - 2 (3/4) x", you wanted to write instead:
 f (x) = - 2 (3/4) ^ x
 So that would be the function that forms a geometric sequence, where the relation between the consecutive terms is 3/4.
 You can test it by dividing f (x) / f (x-1)
 Then you will see that the result of that division will be 3/4.