(a+1)(a+1)=a^2+2a+1
(2+y)(y+3)=2y+6+y^2+3y=y^2+5y+6
(1+x)(1-x)=1-x^2
(x-y)(x+y)=x^2-y^2
(2a+b)(a+2b)=2a^2+4ab+ab+2b^2=2a^2+5ab+2b^2
(a+1)(a+1)=a^2+2a+1
(2+y)(y+3)=2y+6+y^2+3y=y^2+5y+6
(1+x)(1-x)=1-x^2
(x-y)(x+y)=x^2-y^2
(2a+b)(a+2b)=2a^2+4ab+ab+2b^2=2a^2+5ab+2b^2