I have been working on this problem but I cant find anything similar in my book. Not sure how to setup this problem.

Solve the following recurrence relations together with the initial conditions given. $\displaystyle a_n=2a_{n-1}+3a_{n-2}$ for $\displaystyle n\ge 2$, $\displaystyle a_0=1, a_1=7$. Thanks in advance for the help.