a/√b+√b>=2√(a/√b*√b)=2√a
b/√c+√c>=2√(b/√c*√c)=2√b
c/√a+√a>=2√(c/√a*√a)=2√c
相加
a/√b+b/√c+c/√a+√a+√b+√c>=2√(a+2√b+2√c
所以
a/√b+b/√c+c/√a>=√a+√b+√c
a/√b+√b>=2√(a/√b*√b)=2√a
b/√c+√c>=2√(b/√c*√c)=2√b
c/√a+√a>=2√(c/√a*√a)=2√c
相加
a/√b+b/√c+c/√a+√a+√b+√c>=2√(a+2√b+2√c
所以
a/√b+b/√c+c/√a>=√a+√b+√c