a,b,c包含于R+
a^1/2+b^1/2+c^1/2
=√(a^1/2+b^1/2+c^1/2)^2
=√[a+b+c+2(ab)^1/2+2(ac)^1/2+2(bc)^1/2]
≤√[a+b+c+(a+b)+(a+c)+(b+c)]
=√[3(a+b+c)]
=√3
当a=b=c=1/3时,等号成立,有最大值√3
a,b,c包含于R+
a^1/2+b^1/2+c^1/2
=√(a^1/2+b^1/2+c^1/2)^2
=√[a+b+c+2(ab)^1/2+2(ac)^1/2+2(bc)^1/2]
≤√[a+b+c+(a+b)+(a+c)+(b+c)]
=√[3(a+b+c)]
=√3
当a=b=c=1/3时,等号成立,有最大值√3