已知,x,y,z都是实数,且有x+y=2a-1,x平方+y平方=a平方+2a-3,当a为何值时,xy有最小值?我解:算出xy=3/2*a平方-3a+2,所以当a=1时,xy有最小值1/2,但代入x平方+y平方=a平方+2a-3就算出x=y不符了,
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![已知,x,y,z都是实数,且有x+y=2a-1,x平方+y平方=a平方+2a-3,当a为何值时,xy有最小值?我解:算出xy=3/2*a平方-3a+2,所以当a=1时,xy有最小值1/2,但代入x平方+y平方=a平方+2a-3就算出x=y不符了,](/uploads/image/z/8522437-13-7.jpg?t=%E5%B7%B2%E7%9F%A5%2Cx%2Cy%2Cz%E9%83%BD%E6%98%AF%E5%AE%9E%E6%95%B0%2C%E4%B8%94%E6%9C%89x%2By%3D2a-1%2Cx%E5%B9%B3%E6%96%B9%2By%E5%B9%B3%E6%96%B9%3Da%E5%B9%B3%E6%96%B9%2B2a-3%2C%E5%BD%93a%E4%B8%BA%E4%BD%95%E5%80%BC%E6%97%B6%2Cxy%E6%9C%89%E6%9C%80%E5%B0%8F%E5%80%BC%3F%E6%88%91%E8%A7%A3%EF%BC%9A%E7%AE%97%E5%87%BAxy%3D3%2F2%2Aa%E5%B9%B3%E6%96%B9-3a%2B2%2C%E6%89%80%E4%BB%A5%E5%BD%93a%3D1%E6%97%B6%2Cxy%E6%9C%89%E6%9C%80%E5%B0%8F%E5%80%BC1%2F2%2C%E4%BD%86%E4%BB%A3%E5%85%A5x%E5%B9%B3%E6%96%B9%2By%E5%B9%B3%E6%96%B9%3Da%E5%B9%B3%E6%96%B9%2B2a-3%E5%B0%B1%E7%AE%97%E5%87%BAx%3Dy%E4%B8%8D%E7%AC%A6%E4%BA%86%2C)
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