diskritisasi $$P$$t$=$u$$P$$x$+$A$02$P$$x$2+$kP$\backslash$frac$\{\backslash$partial P$\}\{\backslash$partial t$\}=-$u $\backslash$frac$\{\backslash$partial P$\}\{\backslash$partial x$\}+$ A$\_0\backslash$frac$\{\backslash$partial$^2$ P$\}\{\backslash$partial x$^2\}+$ kP