Can we add terms in the differential equation that can help increase the order of the truncation error?
To be precise for the Forward Euler scheme, can we find \( C \) to make \( R \) $\Oof{\Delta t^2}$? $$ \begin{equation} \lbrack D_t^+ \uex + a\uex = C + R \rbrack^n\tp \tag{30} \end{equation} $$