Tofer Carlson's Algebra II Class 

Completing the Square 1 (AoPS)

Completing the Square 2 (AoPS)

Completing the Square 3 (AoPS)

Completing the Square with Unknown Coefficients (AoPS)

Using the Quadratic Formula 1 (AoPS)

Using the Quadratic Formula 2 (AoPS)

Using the Quadratic Formula 3 (AoPS)

The Discriminant (AoPS)