(x-2y)²-(3x+4y)²

问题描述:

(x-2y)²-(3x+4y)²

(x-2y)²-(3x+4y)²
=[(x-2y)+(3x+4y)][(x-2y)-(3x+4y)]
=(4x+2y)(-2x-6y)
=-4(2x+y)(x+3y)