Quadratics
Factorising by Cross Method (Part 1)

Quadratics

Factorising when A = 0

• Sum and product method (part 1)
• Sum and product method (part 2)

Factorising when A ≠ 0

• Cross method (part 1)
• Cross method (part 2)

Factorising special situations​

• Factorising perfect squares
• Factorising difference of two squares (part 1)
• Factorising difference of two squares (part 2)
• ​Factorising by completing the square​

Solving quadratic equations

• Solving basic quadratics
• Null factor law
• Solution by factorisation
• Solution by completing the square
• The quadratic formula

Sketching quadratic equations

• From factorised form
• From vertex form (part 1)
• From vertex form (part 2)
• By completing the square​​

There are some factorable quadratics where a≠1 and there is no way to make a=1 without creating fractions that are difficult to factorise. When faced with these problems there are a number of methods to find the solution, one such method is the cross method, a trial and error based approach.