(2x+y)²-(x+2y)²
解:原式=(2x+y+x+2y)(2x+y-x-2y)
=(3x+3y)(x-y)
=3(x+y)(x-y)
=3(x²-y²)
利用平方差公式:(2x+y-x-2y)(2x+y+x+2y)
=(x-y)(3x+3y)
=3(x+y)(x-y)
= (2x +y +x+2y)(2x+y -x-2y)
=(3x+3y)(x-y)
=3(x+y)(x-y)
(2x+y)²-(x+2y)²
=(2x+y+x+2y)(2x+y-x-2y)
=(3x+3y)(x-y)
=3(x+y)(x-y)