Question

(x-2y)^2-(x-y)×(x+y)-2y^2的算式怎么写？

不会写

Answer 1

（X一2y）^2一（X一y）x（X+y）一2y^2
=X^2一4Xy十4y^2一（X^2一y^2）一2y^2
=X^2一4Xy十4y^2一X^2+y^2一2y2
=一4Xy十3y^2

Answer 2

(x-2y)^2-(x-y)×(x+y)-2y^2
=x^2-4xy+4y^2-x^2+y^2-2y^2
=-4xy+3y^2。