Question

Find an equation for the nth term of the sequence.

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

an = 4 • -4n
an = 4 • -4n + 1
an = -4 • 4n
an = -4 • 4n - 1

Answer 1

could u see any pattern ?

Answer 2

and if you know Geometric sequence,
can you find the common ratio ?

Answer 3

times 4

Answer 4

thats correct!
so the common ratio = r =4

now the first term = a1 = -4

just plug all these in the general geometric series formula
\(\huge a_n = a_1r^{n-1}\)

Answer 5

Oh wow that easier that I thought. Thanks!

Answer 6

yes it is easy :)
welcome ^_^