Find the 7th term in the sequence -1,2,-4,8

Work Shown:

We have a geometric sequence

a = first term = -1

r = common ratio = (second term)/(first term) = 2/(-1) = -2

nth term

a(n) = a*(r)^(n-1)

a(n) = -1*(-2)^(n-1)

Now plug in n = 7 to get the 7th term

a(n) = -1*(-2)^(n-1)

a(7) = -1*(-2)^(7-1)

a(7) = -1*(-2)^6

a(7) = -1*(64)

a(7) = -64

The first seven terms are

-1, 2, -4, 8, -16, 32, -64

To get each new term, we multiply the last term by the common ratio -2