Actually, there is no equation here. You missed the sign "=" and the right side. But if it is= , then the roots are = , = . The difference - (in this order) is = . It is equal to 1 (or -1): = +/-1. Square both sides: (9p^2 - 40q)/4 = 1, or 9p^2 - 40q = 4. It is your equation for p and q.