Solve the initial value problems

$y^{\text{'}}+3y=1,y(0)=1$

$y^{\text{'}}+2xy=x{e}^{-x^2},y(0)=2$

$y^{\text{'}}+7y=e^{3x},y(0)=0$

$x{y}^{\text{'}}+2y=8x^2,y(1)=3$