Question

The general equation for the geometric sequence -1, -2, -4, ... is a n = -1 · 2 n - 1 .

Answer 1

$\text{First term,}~ a = -1\\\\\text{Common ratio,}~ r = 2\\\\\text{Nth term} = ar^{n-1}=-1\cdot 2^{n-1}$