先化简(3x²-4y²)+[-(x²-2xy-y²)]-[-(3x²-

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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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