(x+y)²=1,(x-y)²=11,求x+y与xy的值
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![(x+y)²=1,(x-y)²=11,求x+y与xy的值](/uploads/image/z/7080656-32-6.jpg?t=%28x%2By%29%26%23178%3B%3D1%2C%28x-y%29%26%23178%3B%3D11%2C%E6%B1%82x%2By%E4%B8%8Exy%E7%9A%84%E5%80%BC)
(x+y)²=1,(x-y)²=11,求x+y与xy的值
(x+y)²=1,(x-y)²=11,求x+y与xy的值
(x+y)²=1,(x-y)²=11,求x+y与xy的值
问题:(x+y)²=1,(x-y)²=11,求x+y与xy的值.
解析:(x+y)²=1,x²+2xy+y²=1
(x-y)²=11,x²-2xy+y²=11
两式相减:4xy=-10,得xy=-5/2
(x+y)²=1,开方得:x+y=1或-1