So I was doing this question from the 1967 4U HSC which is as follows:
\text{Express } \dfrac{1-abx^2}{(1-ax)(1-bx)} \text{ in the form: } p + \dfrac{q}{1-ax} + \dfrac{r}{1-bx}
\text{Given that } R_n(x) \text{ is a polynomial, and that:}
1-abx^2 = (1-ax)(1-bx)(1+u_1x + u_2x^2 + ...