a2 – b2 = (a–b) (a+b)

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

a2 – 2ab + b2 = (a–b) 2

a3 + b3 = (a+b) ( a2 –ab + b2 )

a3 – b3 = (a–b) ( a2 +ab + b2 )

x2 +bx +c = (x+m) (x+n)

ax + ay + bx + by = (a+b) (x+y)

x2 +bx +c = (x+r) (x+s)

ab + ac = a (b+c)

an – bn = (a–b) ( an–1 + an–2b + … + bn–1 )

a4 – b4 = ( a2 – b2 ) ( a2 + b2 ) = (a–b) (a+b) ( a2 + b2 )

a3 + b3 + c3 – 3abc = (a+b+c) ( a2 + b2 + c2 –ab –bc –ca )

(a+b) 3 = a3 + 3 a2b + 3a b2 + b3

(a–b) 3 = a3 – 3 a2b + 3a b2 – b3

ax2 +bx +c = (mx+n) (px+q)