Suppose that q(z) = 1, and p(z) = (1 + z)(1 + 3z).
We wish to express q(z)/p(z) in the form
where A and B are constants. To find them, we multiply through by p(z) =
(1 + z)(1 + 3z) and obtain
1 = A(1 + 3z) + B(1 + z)
= (A + B) + (3A + B)z
Im fine up to this point, But according to...