The sequence 4,12,36,108, is a G.P., because `(12)/4=(36)/(12)=(108)/(36)==3,` which is constant.

Explanation

Given,`4,12,36,108`

Let`a=4`

`ar=12`

`ar^2=36`

`ar^3=108`

For a G.P`ar/a=(ar^2)/(ar)=(ar^3)/(ar^2)`

or,`(12)/4=(36)/(12)=(108)/(36)==3,`