d^2[u]+D[v]=2 and 4u+D[v]=6

D^2[u]+D[v]=2
-4u-D[v]=16
Add and then D^2[u]-4u=-4

u''-4u=-4
Auxiliary equation r^2-4=-4 so (r-2)(r+2)=0 so r= +/-2
uh(t)=c1e^(2t) + c2e^(-2t)
up(t)=A cos t + B cos t

This is where I am stuck, what do I do next?