1. The problem statement, all variables and given/known data Ok, so I have a 2nd order differential equation, I can get the complimentary function no problem, its getting numerical values for terms in the particular integral that I can't do. 2. Relevant equations y'' - y' - 2y = t2 3. The attempt at a solution Complimentiary function: y(t) = Ae2t + Be-t All fine and dandy, now particular interal for t2: ypi(t) = At2 + Bt + C Now we find the first and second order derivatives: First: 2At + B Second: 2A Now substituting these terms back into original equation: 2A - (2At + B) - 2(At2 + Bt + C) = t2 This is where I'm stuck, I'm looking at my notes for the next bit: We can find A, B and C by equating terms, so: t2: -2A -1 t: -2A - 2B = 0 1: 2A - b - 2C = 0 I don't understand that at all, can someone explain that a bit further?