(x+2y)²-(x+y)(3x-y)-5y²,其中x=-2,y=2分之1
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![(x+2y)²-(x+y)(3x-y)-5y²,其中x=-2,y=2分之1](/uploads/image/z/1630943-71-3.jpg?t=%EF%BC%88x%2B2y%EF%BC%89%26%23178%3B-%EF%BC%88x%2By%EF%BC%89%EF%BC%883x-y%EF%BC%89-5y%26%23178%3B%2C%E5%85%B6%E4%B8%ADx%3D-2%2Cy%3D2%E5%88%86%E4%B9%8B1)
(x+2y)²-(x+y)(3x-y)-5y²,其中x=-2,y=2分之1
(x+2y)²-(x+y)(3x-y)-5y²,其中x=-2,y=2分之1
(x+2y)²-(x+y)(3x-y)-5y²,其中x=-2,y=2分之1
先化简,再代入啊
(x+2y)²-(x+y)(3x-y)-5y²
=x²+4xy+4y²-3x²+y²-2xy-5y²
=-2x²+2xy
将x=-2,y=1/2代入
=-10
原式=x²+4xy+4y²-3x²-2xy+y²-5y²
=-2x²+2xy
=-8-2
=-10