Can someone explain how they get the answer.

For the following geometric sequence, find the recursive formula. {-80, 20, -5, } i need : ')

1. writing an equation for an exponential function by 2. a piece of paper that is 0.6 millimeter thick is folded. write an equation for the thickness t of the paper in millimeters as a function of the number n of folds. the equation is t(n)= 3. enter an equation for the function that includes the points. (-2, 2/5) and (-1,2)

Plz ( true - false) all triangles have interior angles whose measure sum to 90.