d^2x/[dt]^2 -4 dx/dt=7-3e^4t

Could someone also help me with this? Find the particular solution. I find trouble knowing what trial to use because of the 7-3e^4t. My Tutor said to use a constant with the particular trial >>xp(t)=Ate^4t. Can you show me how to get the A,B and constant value please. Thanx