Solution
= Solution
The first <initial condition> gives $A=1$. The original first equation gives $u'(0)=-3u(0)+v(0)=-2$, whereas the <general solution> gives $u'(0)=B-A$. Thus $B=-1$ and
$$
\boxed{u(t)=e^{-t}(\cos t-\sin t)}.
$$
The corresponding $v=e^{-t}(\cos t-3\sin t)$ has $v(0)=1$, checking the other <initial condition>.