We are given
geometric sequence
3,9,27,81,...
we can see that
first term is 3
so,
[tex] a_1=3 [/tex]
second term is 9
[tex] a_2=9 [/tex]
we can also write it as
[tex] a_2=3*3 [/tex]
we can replace 3 as a1
[tex] a_2=3a_1 [/tex]
Similarly , we have
third term is 27
[tex] a_3=27 [/tex]
we can also write it as
[tex] a_3=3*9 [/tex]
[tex] a_3=3a_2 [/tex]
so, for nth term
[tex] a_n=3a_n_-_1 [/tex] for n>1.........Answer