计算:(2x-y)2-4(x-y)(x+2y)

问题描述:

计算:(2x-y)2-4(x-y)(x+2y)

原式=4x2-4xy+y2-4(x2+xy-2y2)=4x2-4xy+y2-4x2-4xy+8y2=-8x+9y2