(x-2y)²-(3x+4y)²
问题描述：
(x-2y)²-(3x+4y)²
答
求什么 ？
答
(x-2y)²-(3x+4y)²
=(x-2y+3x+4y)(x-2y-3x-4y)
=(2y+4x)(-6y-2x)
答
(x-2y)²-(3x+4y)²
=[(x-2y)+(3x+4y)][(x-2y)-(3x+4y)]
=(4x+2y)(-2x-6y)
=-4(2x+y)(x+3y)