  We analyze the application of the "tridiagonal representation approach" (TRA)
to the Schr\"{o}dinger equation for some simple, exactly-solvable,
quantum-mechanical models. In the case of the Kratzer-Fues potential the
mathematical reasoning appears to exhibit a serious flaw that invalidates the
result and the expression for the energy does not appear to be correct. We also
show that the well known Frobenius method, which resembles the TRA, is far
simpler, clearer and more elegant; in addition to give the correct result.
