已知x^2+y^2=4,求2xy/(x+y-2) 的最小值
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已知x^2+y^2=4,求2xy/(x+y-2) 的最小值
已知x^2+y^2=4,求2xy/(x+y-2) 的最小值
已知x^2+y^2=4,求2xy/(x+y-2) 的最小值
已知x²+y²=4,求2xy/(x+y-2)的最小值.
由于(x-y)²≥0,展开得:2xy≤x²+y²,则有:
x²+y²+2xy≤2(x²+y²)
(x+y)²≤2(x²+y²)=8
得:-2√2≤x+y≤2√2,
所以有:
2xy/(x+y-2)
=(x²+y²+2xy-4)/(x+y-2)
=[(x+y)²-4]/(x+y-2)
=(x+y+2)(x+y-2)/(x+y-2)
=x+y+2≥2-2√2
因此,2xy/(x+y-2)的最小值是2-2√2.