2. The sum of the first term and the second term of a geometric sequence is 30, the sum of the third term and the fourth term is 120, find the sum of the fifth term and the sixth term.
2. Solution Let the first term be $\mathrm{a}$, and the common ratio be $\mathrm{q}$. Then
$$
\begin{array}{l}
a+a q=30, \\
a q^{2}+a q^{3}=120 .
\end{array}
$$

From (1) and (2), we get $q= \pm 2$. When $q=2$, $a=10$, at this time the sum of the 5th and 6th terms is 480. When $q=-2$, $a=-30$, at this time the sum of the 5th and 6th terms is 480.