>>453
相加-相乗平均で
(左辺)≧2{1/(1+xx)(1+x)}{1/(1+yy)(1+y)}{1/(1+zz)(1+z)}
＝2{(1-x)/(1-x^4)}{(1-y)/(1-y^4)}{(1-z)/(1-z^4)}
≧(右辺).