答：12（x+y)的平方+11（x+y)(x-y)+2(x-y)的平方=12(x+y)²+11(x+y)(x-y)+2(x-y)²=12x²+24xy+12y²+11x²-11y²+2x²-4xy+2y²=25x²+20xy+3y²=(5x+y)(5x+3y)