(2) (x+y+z) (x+y -z) = {(x+y)+z} {(x+y) -z} = (x+y) square-z square = x square +2xy+y square-z square.

(3){(x+y)square-(x-y)square }⊙(2xy)= {(x square+2xy+y square)-(x square-2xy+y square)}⊙

(2xy) = (x square +2xy+y square -x square +2xy-y square) ÷ (2xy) = 4xy ÷ (2xy) = 2.

(4)a's square (a+ 1) square -2(a's square -2a+4) = A's square (A's square +2a+ 1)-2a's square +4a-8 = A4's square +2a's cube +2a's square+4A -2a's square.