>>536
　>>542のスレから転記

aa+1+1+1≧4√a、 bb+1+1+1≧4√b、 cc+1+1+1≧4√c,　　（←相加-相乗平均)

(左辺) ≦ (1/2) {(bb/a)^(1/4) + (cc/b)^(1/4) + (aa/c)^(1/4)}

＝ (1/2) (1/abc)^(1/4) {(bbbc)^(1/4) + (ccca)^(1/4) + (aaab)^(1/4)}

≦ (1/2) (1/abc)^(1/4) {(b+c+a)^3 (c+a+b)}^(1/4)　　(←コーシー)

＝ (a+b+c)/2 (1/abc)^(1/4)