 He had the following rules for how to decode  the effect of the coefficients on their constituents: (1) for the coefficient \(m/m\) with \(m \neq 0\) the constituent is kept in the solution; (2) for \(0/m\) with \(m \neq 0\) the constituent is deleted; (3) the coefficient \(0/0\) is changed into an  arbitrary parameter; and (4) any other coefficient indicated that the constituent  was to be removed and set equal to 0. This use of formal division and formal expansion is best regarded as a clever mnemonic device.