Computation of dparu(u)

> dparu1:=collect(subs(d(z)=0,dg),p);

The next three steps are a bit of 'sleight of hand' to get Maple to remove the appropriate terms... namely those with a p in the numerator, and no p's in the denominator.

> dparuromeo:=simplify(p*dparu1);

> dparulist:=convert(dparuromeo,list);

> dparujuliet:=remove(has,dparulist,{p^2,p^3,p^4});

> dparu2:=convert(dparujuliet,`+`)/p;

Now we simplify dparu2, set it equal to zero, and solve for d(u). This is then dparu(u).

> dparuu:=solve(dparu2=0,d(u));

>