因式分解36a²-(a²+9)² 49（x-y）²-25（x+y）²

题目

因式分解36a²-(a²+9)² 49（x-y）²-25（x+y）²

答案

36a^2-(a^2+9)^2
=(6a-a^2-9)(6a+a^2+9)
=-(a-3)^2(a+3)^2
49(x-y)^2-25(x+y)^2
=(7x-7y-5x-5y)(7x-7y+5x+5y)
=(2x-12y)(12x-2y)
=4(x-6y)(6x-y)