How can I solve this equation $\displaystyle x''-x=(1+e^{t})^{-1}$ using the method of variation of parameters?Using the auxiliary equation the roots are $\displaystyle r_{1}=0$ and$\displaystyle r_{2}=1$.

I don't know if I'm suppose to look for a solution of the form $\displaystyle x(t)=p+q*e^{x}$ manly because the initial equation has o 1+... after the equal sign .Can someone please help me?