Solve the equation

$$\ddot{y}+\dot{y}-2 y=e^{-t}$$

subject to the conditions $y(t)=\dot{y}(t)=0$ at $t=0$. Solve the equation

$$\ddot{y}+\dot{y}-2 y=e^{t}$$

subject to the same conditions $y(t)=\dot{y}(t)=0$ at $t=0$.