已知M=2x²y-6xy+3,N=3xy-x²y+1,当xy不等于0时,2M-7N=-1恒成立,则x的值为?
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![已知M=2x²y-6xy+3,N=3xy-x²y+1,当xy不等于0时,2M-7N=-1恒成立,则x的值为?](/uploads/image/z/1682911-55-1.jpg?t=%E5%B7%B2%E7%9F%A5M%3D2x%26%23178%3By-6xy%2B3%2CN%3D3xy-x%26%23178%3By%2B1%2C%E5%BD%93xy%E4%B8%8D%E7%AD%89%E4%BA%8E0%E6%97%B6%2C2M-7N%3D-1%E6%81%92%E6%88%90%E7%AB%8B%2C%E5%88%99x%E7%9A%84%E5%80%BC%E4%B8%BA%3F)
已知M=2x²y-6xy+3,N=3xy-x²y+1,当xy不等于0时,2M-7N=-1恒成立,则x的值为?
已知M=2x²y-6xy+3,N=3xy-x²y+1,当xy不等于0时,2M-7N=-1恒成立,则x的值为?
已知M=2x²y-6xy+3,N=3xy-x²y+1,当xy不等于0时,2M-7N=-1恒成立,则x的值为?
2M-7N=-1
∴ 2(2x²y-6xy+3)-7(3xy-x²y+1)=-1
4x²y-12xy+6-21xy+7x²y-7=-1
11x²y-33xy=0
11xy(x-3)=0
∵xy≠0
∴x-3=0
x=3