Higher GCSE. y=ax^2 + bx - c: A 'new method' of factorising they do not teach in schools. Adjusts the constant to include the coefficient of x^2 so that the calculations reflect its influence. Correction is then applied at the end to return the values to what they should be. Removes guess and test approach normally taught. Did not wish to confuse you so I did not explain why it works.