Question 39
Let $S$ be the sum of the first nine terms of the sequence
$$
\begin{gathered} x+a,\quad x^2+2a,\\ x^3+3a,\quad\ldots. \end{gathered}
$$
Then $S$ equals:
$$
\begin{gathered} x+a,\quad x^2+2a,\\ x^3+3a,\quad\ldots. \end{gathered}
$$
Then $S$ equals: