先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=-2 y=二分之一
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![先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=-2 y=二分之一](/uploads/image/z/469589-5-9.jpg?t=%26%238203%3B%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%9C%A8%E6%B1%82%E5%80%BC%5B%28x-2y%29%26%23178%3B-%EF%BC%88x-y%EF%BC%89%EF%BC%883x%2By%EF%BC%89-5y%26%23178%3B%5D%C3%B7%EF%BC%88-2x%EF%BC%89%2C%E5%85%B6%E4%B8%ADx%3D-2+y%3D%E4%BA%8C%E5%88%86%E4%B9%8B%E4%B8%80)
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先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=-2 y=二分之一
先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=-2 y=二分之一
先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=-2 y=二分之一
解
[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x)
=[x²-4xy+4y²-(3x²+xy-3xy-y²)-5y²]÷(-2x)
=(x²-4xy+4y²-3x²+2xy+y²-5y²)÷(-2x)
=(-2x²-2xy)÷(-2x)
=x+y
=-2+1/2
=-3/2
[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x)
=[(x²-4xy+4y²)-(3x²-2xy-y²)-5y²]÷(-2x)
=(x²-4xy+4y²-3x²+2xy+y²-5y²)÷(-2x)
=(-2x²-2xy)÷(-2x)
=x+y
=-2+1/2
=-3/2
原式=(x²-4xy+4y²-3x²+2xy+y²-5y²)/(-2x)
=x+y