wow you totally got the question. thanks alot. i see it clearly now :)
LCKurtz: Q(x,t) is just force acting on the string, so gravity in most cases. i got the answer now, sorry for not being more precise.
thanks for taking a look. still stumped. Ue(x) is the sagged equilibrium position ( when Q(x,t)=-g and the boundary conditions are u(0)=0 and u(L)=0 or fixed boundary/ends of the string). i hope that clarifies it a bit?
how do i show that v(x,t)=u(x,t)-ue(x) satisfies the wave equation? =(
i get that ue(x)=gx2/2c2 + ax + b where a and x are just constants but how does this satisfy the wave equation?