先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²)其中x=三分之一,y=3
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![先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²)其中x=三分之一,y=3](/uploads/image/z/2742715-19-5.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%9C%A8%E6%B1%82%E5%80%BC2x%26%23178%3B-y%26%23178%3B%2B%282y%26%23178%3B-x%26%23178%3B%29-%28x%26%23178%3B%2B2y%26%23178%3B%29%E5%85%B6%E4%B8%ADx%3D%E4%B8%89%E5%88%86%E4%B9%8B%E4%B8%80%2Cy%3D3)
先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²)其中x=三分之一,y=3
先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²)其中x=三分之一,y=3
先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²)其中x=三分之一,y=3
2x²-y²+(2y²-x²)-(x²+2y²)
=2x²-y²+2y²-x²-x²-2y²
=-y²
=-3²
=-9