Really struggling with this one dy/dt = 2t(y + 1) + 2at^3 where a is a parameter. Find the general solution of the ODE when a = 0 using the fact that it is separable. After this, use the fact that that it is a linear ODE to find an integrating factor, and use this method (different to what you just did) to solve the ODE for the case where a = 0 and also for the case where a =/= 0. I've tried separating, but I keep getting it wrong. I can get to integrating where it is dy/dx - 2ty = 2t + 2at^3 but I don't know if this is right or where to go.