Answer:
[tex]S_3=39[/tex]
Step-by-step explanation:
The nth term of the sequence is
[tex]a_n=3(3)^{n-1}[/tex]
To get the first term, substitute n=1,
[tex]a_1=3(3)^{1-1}=3[/tex]
To get the second term, substitute n=2,
[tex]a_2=3(3)^{2-1}=9[/tex]
To get the third term, substitute n=3,
[tex]a_3=3(3)^{3-1}=27[/tex]
The sum of the first three terms is
[tex]S_3=3+9+27=39[/tex]
We could also use the formula
[tex]S_n=\frac{a_1(r^n-1)}{r-1}[/tex] to get the same result.
