(5x²-3y²)-[﹙5x²-2xy-y²﹚-﹙x²-2xy+3y²)]

问题描述:

(5x²-3y²)-[﹙5x²-2xy-y²﹚-﹙x²-2xy+3y²)]

(5x²-3y²)-[5x²-2xy-y²-x²+2xy-3y²]
=(5x²-3y²)-[4x²-4y²]
=x²-y²
你连这也不会,读几年级 啊?