Question

Find an equation for the nth term of the sequence.

-4, -16, -64, -256, ...

Answer 1

this is a geometric sequence  with first term a1 = -4 and common ratio r = 4

so nth term  = a1* r^(n-1)

                   = -4 *4^(n-1)

Answer 2

Common ratio = 4
Starts at -4

So the equation is n = -4 *4^(n-1)