已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4hgfhg
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已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4hgfhg已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4hgfhg已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥1
已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4hgfhg
已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4
hgfhg
已知X,Y∈R+,且X+Y=1,求证:XY+1/XY≥17/4hgfhg
(x+1/x)(y+1/y)
=xy+x/y+y/x+1/(xy)
=(x/y+y/x)+xy+1/(xy)]
依均值不等式x/y+y/x>=2.(*)
因为xy=0时,在X=1时有极小值Y=2,在X>1时递增,在0=2+17/4=25/4.
x/y=y/x,xy=1/4--->x=y=1/2,时“=”成立.证完
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