（）+x^2-xy+2y^2=2x^2+xy+3y^23x^2+xy-7y^2-( )=x^2-2xy+y^2

分类: 作业答案 • 2021-12-19 11:02:22

问题描述：

（）+x^2-xy+2y^2=2x^2+xy+3y^2
3x^2+xy-7y^2-( )=x^2-2xy+y^2

答

（）=2x^2+xy+3y^2-x^2+xy-2y^2=x^2+2xy+y^2
()=3x^2+xy-7y^2-x^2+2xy-y^2 =2x^2+3xy-8y^2

（ ）+x^2-xy+2y^2=2x^2+xy+3y^23x^2+xy-7y^2-( )=x^2-2xy+y^2