a2x2+b2y2-2ax-2by+2abxy
=(a2x2+2abxy+b2y2)-(2ax+2by)
=(ax+by)^2-2(ax+by)
=(ax+by)(ax+by-2)
x3+6x2+11x+6
=x^3+x^2+5x^2+5x+6x+6
=x^2(x+1)+5x(x+1)+6(x+1)
=(x+1)(x^2+5x+6)
=(x+1)(x+2)(x+3)
x2+6xy+9y2-16x-48y-36
=(x^2+6xy+9y^2)-(16x+48y)-36
=(x+3y)^2-16(x+3y)-36
=(x+3y+2)(x+3y-18)