Problem solving

Harder factorisation

Quadratic equations

Difference of two squares

Quadratic factorising

Factorisation

Squaring a bracket

(x+2)^2
= (x+2)(x+2)
= x^2+2x+2x+4

(x+a)^2 = x^2+2ax+a^2

(x-a)^2 = x^2-2ax-a^2

(x+a)(x-a) = x^2-a^2

Recall Foil

Foil: e.g,          (x+2)(x-3) = x^2 -3x+2x-6
                        (3a-2b)(4a+3b) = 12a^2+9ab-8ba-6b^2
                                                  = x^2-x-6 

                                                           = 12a^2+ab-6b^2