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)
因式分解36（x-y）²-49（x+y）²
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)