(2x-y)^2-4(x-y)(x+2y)答案是9y^2-8xy```

(2x-y)^2-4(x-y)(x+2y)答案是9y^2-8xy```
(2x-y)^2-4(x-y)(x+2y)
答案是9y^2-8xy```

(2x-y)^2-4(x-y)(x+2y)答案是9y^2-8xy```
4x^2+y^2-4xy-4(x^2-xy+2xy-2y^2)
展开化简吧!

(2x-y)^2-4(x-y)(x+2y)
=4x^2-4xy+y^2-4x^2-4xy+8y^2
=8y^2-8xy
=8y(y-x)

不会

(2x-y)^2-4(x-y)(x+2y)
=(4x^2-2xy+y^2)-4x(x^2-xy+2xy-2y^2)
=4x^2-2xy+y^2-4x^2+4xy-8xy+8^2
=-6xy+9y^2
展开,合并同类项