## Pages

### The formula

(a + b)2 = a2 + b2 + 2ab

#### Working forwards - Expansion

For example, the expression (2x + 3y)2 can be expanded as follows:
= (2x)2 + (3y)2 + 2(2x)(3y)
= 4x2 + 9y2 + 12xy

#### Working backwards - Factorization

For example, the expression x2 + 100y2 + 20xy can be factored as follows:
x2 + (10y)2 + 2(x)(10y)
On comparing it with a2 + b2 + 2ab
(x + 10y)2
.. which is the factored form.