Definition:Quadratic Irrational/Reduced/Associated

Definition
Let $\alpha$ be a reduced quadratic irrational expressed as:
 * $\alpha = \dfrac{P + \sqrt D} Q$

Then $\alpha$ is associated to $D$ $Q$ divides $D - P^2$.

Also see

 * Definition:Quadratic Equation
 * Quadratic Irrational is Root of Quadratic Equation