I got two DE:s that I have been playing with this weekend, without getting them right.
One of them is:

1. (d^2 u/ dx^2) =4a^2*b^2*c^2 *(du/dt) where a=8, b=4, c=9 ( my constants)
conditions: du/dx(0,t)=du/dx(pi,t)=0
and initial conditions: u(x,0)=(a+5b+c)+(2a+b)cos(abcx)+(ab+3c)cos(3abcx) 0<x<pi
and a=8, b=4, c=9

please help me...
I get problems even though I have been told which way to solve it.
If any one could give me the solution, I would appreciate it alot..

Best Regards,
Daniel