(x+\frac{1}{2}y)^2=x^2+2*x*\frac{1}{2}y+(\frac{1}{2}y)^2=x^2+xy+\frac{1}{4}y^2
(a-3b)^2=a^2-2*a*3b+(3b)^2=a^2-6ab+9b^2
(3x+2y)^2=(3x)^2+2*3x*2y+(2y)^2=9x^2+12xy+4y^2
(3x+2)^2=(3x)^2+2*3x*2+2^2=9x^2+12x+4
(\sqrt3-y)^2=(\sqrt3)^2-2*\sqrt3*y+y^2=3-2\sqrt3y+y^2
(3x-2)^2=9x^2-12x+4