已知x²+y²=2,xy=1/2求代数式(2x²-y²-3xy)-(x²-2y²+xy)的值
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![已知x²+y²=2,xy=1/2求代数式(2x²-y²-3xy)-(x²-2y²+xy)的值](/uploads/image/z/1022252-68-2.jpg?t=%E5%B7%B2%E7%9F%A5x%26%23178%3B%2By%26%23178%3B%3D2%2Cxy%3D1%2F2%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F%282x%26%23178%3B-y%26%23178%3B-3xy%29-%28x%26%23178%3B-2y%26%23178%3B%2Bxy%29%E7%9A%84%E5%80%BC)
已知x²+y²=2,xy=1/2求代数式(2x²-y²-3xy)-(x²-2y²+xy)的值
已知x²+y²=2,xy=1/2求代数式(2x²-y²-3xy)-(x²-2y²+xy)的值
已知x²+y²=2,xy=1/2求代数式(2x²-y²-3xy)-(x²-2y²+xy)的值
原式=2x²-y²-3xy-x²+2y²-xy
=x²+y²-4xy
=2-4×1/2
=0