What is the explicit rule for this geometric sequence? a1=-15; an=1/5•an-1

Option A is correct.

Step-by-step explanation:

Given: ;

for n = 2

=

for n =3

=

Simlarly , for n =4

=

and so on...

Common ratio(r) states that for a geometric sequence or geometric series, the common ratio is the ratio of a term to the previous term.

we have;  

Now; by recursive formula for geometric series:

where is the first term and r is the common ratio:

Substitute the value of  and  

we have;

therefore, the explicit rule for the geometric sequence is;