Question: Display of differentials Quantum theory.

I am modelling a particle in a 2D square well as such; K_op:= psi -> diff(psi, x$2)+diff(psi, y$2)+(2*m*E/(hbar^2))*psi=0; But when I try to view the K_op maple only displays the 2mE/hbar^2 part equals zero.
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