=[(2x+y)+(x-2y)][(2x+y)-(x-2y)]
=(3x-y)(x+3y)
首先将2x+y和x-2y看成一个整体,应用平方差公式算出
(2x+y)²-(x-2y)²
=[(2x+y)+(x-2y)][(2x+y)-(x-2y)]
紧接着去括号就行了
解:(2x+y)²-(x-2y)²
=[(2x+y)+(x-2y)][(2x+y)-(x-2y)]
=(3x-y)(x+3y)
:(2x+y)^2-(x-2y)^2
=(2x+y+x-2y)(2x+y-x+2y)
=(3x-y)(x+3y)
(2x+y)^2-(x-2y)^2=【2x+y-x+2y]*(2x+y+x-2y)=(x+3y)*(3x-y)=3(x^2)+8xy-3(y)^2