Question

Find an explicit rule for the nth term of the sequence.

-3, -15, -75, -375, ...

Answer 1

what have you tried?

could you figure out the common ratio?

Answer 2

common ratio = 2nd term/ 1st term = 3rd term/ 2nd term = ... and so on

Answer 3

common ratio = 5

Answer 4

yes, thats correct :)

r=5
and the first term is a1= -3


just use this general formula for the n'th term of geometric sequence,
\(\large S_n = a_1 r^{n-1}\)
plug in values!

Answer 5

a_n = -3 * 5^n-1, that was easy peezy

Answer 6

yes! quite easy :)