先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)] 再求值,其中x=-1 y=-2
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![先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)] 再求值,其中x=-1 y=-2](/uploads/image/z/1808861-5-1.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%283x%26%23178%3B-4y%26%23178%3B%29%2B%5B-%28x%26%23178%3B-2xy-y%26%23178%3B%29%5D-%5B-%283x%26%23178%3B-2xy-y%26%23178%3B%29%5D+%E5%86%8D%E6%B1%82%E5%80%BC%2C%E5%85%B6%E4%B8%ADx%EF%BC%9D-1+y%EF%BC%9D-2)
先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)] 再求值,其中x=-1 y=-2
先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)] 再求值,其中x=-1 y=-2
先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)] 再求值,其中x=-1 y=-2
(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-2xy-y²)]
=3x²-4y²-x²+2xy+y²+3x²-2xy-y²
=5x²-4y²
=5x(-1)²-4x(-2)²
=5-16
=-11
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原式=3x²-4y²-x²+2xy+y²+3x²-2xy-y²
=5x²-4y²
=5*1-4*4
=-11