Khan Academy

Systems of equations with substitution: coins (K-A)

Discriminant for types of solutions for a quadratic (K-A)

Discriminant of quadratic equations (K-A)

Using the quadratic formula: number of solutions (K-A)

Completing the square (K-A)

Solving quadratics by completing the square: no solution (K-A)

Worked example: Completing the square (intro) (K-A)

Worked example: completing the square (leading coefficient ≠ 1) (K-A)

Worked example: Rewriting expressions by completing the square (K-A)

Worked example: Solving equations by completing the square (K-A)

Solving quadratic equations by factoring (old) (K-A)

Solving quadratics by factoring. (K-A)

Solving quadratics by factoring: leading coefficient ≠ 1 (K-A)

Solving quadratics using structure (K-A)

Strategy in factoring quadratics (part 1 of 2) (K-A)

Strategy in factoring quadratics (part 2 of 2) (K-A)

Quadratics by taking square roots: with steps (K-A)

Solving quadratics by taking square roots examples (K-A)

Solving quadratics by taking square roots. (K-A)

Solving quadratics by taking square roots: challenge (K-A)

Solving quadratics by taking square roots: strategy (K-A)

Zero product property (K-A)

Proof of the quadratic formula (K-A)

The quadratic formula (K-A)

Using the quadratic formula (K-A)