hi guys, having trouble completing this equation

du/dt + 2du/dx=-u

solve for u(x,t)

for initial conditions t=0 and u=1 for x<0 and u=0 for x>0

once solving the equation do i give 2 solutions? one for u=1 and the other for u=0?

if any one has an idea of how to get started with the diff equation it would be much appreciated.

thanks in advance