Find the general solution $to$ the following higher order nonhomogeneous

linear differential equations:

$(a)y^{(4)}-y=3t+sin(t)$;

$(b)y^{\text{'}\text{'}\text{'}}-3y^{\text{'}\text{'}}+2y^{\text{'}}=t+e^t\{$:$y(0)=1,y^{\text{'}}(0)=-\frac{1}{4},y^{\text{'}\text{'}}(0)=-\frac{3}{2}).$