Question

For the following geometric sequence, find the recursive formula. {-80, 20, -5, ...}

Answer 1

For the geometric sequence, it has two forms of formula


We are interested in the recursive formula now


{-80, 20, -5, ...}

The common ratio is (20/-80)=(-5/20)=-1/4=-0.25

So our recursive formula would be$a_n=a_{n-1}*(-0.25)=a_{n-1}*(- \frac{1}{4} )$

I hope that helps!