### The formula

(a + b)^{2}= a^{2}+ b^{2}+ 2ab

#### Working forwards - Expansion

For example, the expression (2x + 3y)^{2}can be expanded as follows:

= (2x)^{2}+ (3y)^{2}+ 2(2x)(3y)

= 4x^{2}+ 9y^{2}+ 12xy

#### Working backwards - Factorization

For example, the expression x^{2}+ 100y

^{2}+ 20xy can be factored as follows:

xOn comparing it with a^{2}+ (10y)^{2}+ 2(x)(10y)

^{2}+ b

^{2}+ 2ab

(x + 10y).. which is the factored form.^{2}