1. The problem statement, all variables and given/known data y'' -6y' + 9y = f(t) f(t)= 0, 0<t<1 1, 1<t<3 0, t>3 2. Relevant equations 3. The attempt at a solution Turning it to heaviside functions I get: y'' -6y' + 9y = u1 - u3 and I solve. in the answers it should be: y(t) = 2tet + u1(1/9 - 1/9e3(t-1)+ 1/3(t-1)e3(t-1)). where did u3 go in the answers? why doesn't it appear? the u1 I can get just like that, but I can't seem to figure out where the u3 went and why there is a 2tet in there.