The Non-Homogeneous Differential Equation
$$Ly=R$$ Where $$ L=F(D)= \sum_i a_iD^i $$
Is solved with the way below.
$$ Ly=R \Rightarrow y=\frac{R}{L}=\frac{R}{F(D)}$$
Then we expand the qiotient $ \frac{1}{F(D)}$ into Taylor Series in the neighborhood of 0 (McLaurin).
In order to expand F(D) we have to give $D=\frac{d}{dx} $ a value. How can we give a differential operator a value?