To find the common ratio of the sequence, divide each of the elements of the sequence by the element that precedes it:
[tex]\begin{gathered} \frac{-9}{3}=-3 \\ \frac{27}{-9}=-3 \\ \frac{-81}{27}=-3 \end{gathered}[/tex]
Since the quotient is always -3, then the common ratio is equal to -3.
To find the fifth term of the sequence, multiply the fourth term, which is -81, times -3:
[tex]-81\times-3=243[/tex]
Once that we know the first five terms of the sequence, add them to find their sum:
[tex]\begin{gathered} 3-9+27-81+243 \\ =-6+27-81+243 \\ =21-81+243 \\ =-60+243 \\ =183 \end{gathered}[/tex]
Therefore:
The common ratio of the sequence is -3.
The sum of the first five terms of the sequence is 183.
