Sum and Product of roots. Video tutorial, web notes.
Completing the square. Video tutorial, notes, practice, answers. Harder examples
The discriminant and its uses. Video 1, video 2 , video 3
Factor and remainder theorem. Video tutorial 1, tutorial 2
Algebraic long division. Factorising cubics. Video 1 . Video 2
Comparing coefficients. Video tutorial
Complex numbers
A history for those interested
Complex numbers in modulus and argument form, and argand diagrams
De Moivre's Theorem and Polar form