若x2+y2=25,x+y=7,则x-y=______.
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若x2+y2=25,x+y=7,则x-y=______.
![若x2+y2=25,x+y=7,则x-y=______.](/uploads/image/z/17347808-56-8.jpg?t=%E8%8B%A5x2%2By2%3D25%EF%BC%8Cx%2By%3D7%EF%BC%8C%E5%88%99x-y%3D______%EF%BC%8E)
∵x2+y2=25,x+y=7
∴(x+y)2=x2+2xy+y2=49,
解得2xy=24,
∴(x-y)2=x2-2xy+y2=25-24=1,
∴x-y=±1.
故答案是:±1.
∴(x+y)2=x2+2xy+y2=49,
解得2xy=24,
∴(x-y)2=x2-2xy+y2=25-24=1,
∴x-y=±1.
故答案是:±1.
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