Dear all,
A differential equation is to be solved. In order to simplify a substitution is made. This leads to a form with u'' and u. The factor of u has a few terms. One of these is of the type x-x. When I try to simplify, then Mathematica does not eliminate this term. Below is the script tst.m. When run the term is seen close to the end as rho^2-rho^2.
Q.: how do I proceed to make M. remove this zero term?
Regards,
ChG

(* Clear all variables for a pristine state *)
ClearAll[Evaluate[Context[] <> "*"]]

rho = \[Rho];
rho0 = Subscript[rho, 0];
rho2 = Superscript[rho, 2];
expr := D[ u[rho], {rho,2} ]  - (-1 + HoldForm[l (l + 1)]/rho2 + rho0^2*rho2) u[rho];

eqn=expr /. u -> Function[rho, rho^(l+1) * Exp[-rho0*rho^2/2]*v[rho] ]
eqn2=Simplify[eqn]

(* Can it do better? *)
eqn3=FullSimplify[eqn2]