Find the next three terms in the geometric sequence: 4, -12, 36, -108

Aman steps out of a plane at a height of 4,000m above the ground falls 2,000m very quickly and then opens his parachute and slowly falls the remaining 2000m to the ground what height above the ground would be the best choice for a reference point

How can you decide witch operations to use to slice a two step equation

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie