36(x+y)²-49(x-y)²
=[6(x+y)+7(x-y)][6(x+y)-7(x-y)]
=(6x+6y+7x-7y)(6x+6y-7x+7y)
=(13x-y)(-x+13y)
=-(13x-y)(x-13y)
36（x+y)的平方-49（x-y)的平方
36(x+y)²-49(x-y)²
=[6(x+y)+7(x-y)][6(x+y)-7(x-y)]
=(6x+6y+7x-7y)(6x+6y-7x+7y)
=(13x-y)(-x+13y)
=-(13x-y)(x-13y)