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

a2-b2 = (a+b)(a-b)

(a-b)3 = a3-3a2b+3ab2-b3

if: xa=xb, then: a=b (except if: x=1)

x-a = 1/xa   AND  1/x-a = xa

(xa)(xb) = xa+b

(xa)b = xab

xa/xb = xa-b = 1/xb-a

x0 = 1

(xa)(ya) = (xy)a

(x/y)a = xa/ya

(x+a)(x+b) = x2+ax+bx+ab = x2+(a+b)x+ab