ANSWER
The required equation is:
[tex]a_n=5( - \frac{3}{5} )^{n-1}[/tex]
EXPLANATION
The given sequence is
[tex]5, -3 , \frac{9}{5} [/tex]
The first term of the sequence is ;
[tex]a_1=5[/tex]
The common ratio is the subsequent term previous term of any two consecutive terms. This implies that;
[tex]r = \frac{ - 3}{5} [/tex]
The nth term of the sequence is
[tex]a_n=a_1(r)^{n-1}[/tex]
We substitute the terms to obtain;
[tex]a_n=5( - \frac{3}{5} )^{n-1}[/tex]