17/08/28 01:54:30.17 4VsD2YTN.net
>>679 (5)
a/c=y, b/a=z, c/b=x とおくと xyz=1.
(a-b)(b-c)(c-a)/abc =（a/b +b/c +c/a）-（c/b +a/c +b/a）=（xy+yz+zx）-（x-y-z),
(左辺）-（右辺）=（xx+yy+zz）-2(xy+yz+zx）+2(x-y-z）-3
=（x+y+z)^2 -4(xy+yz+zx）+2s -3
=｛F_1(x,y,z) -9xyz}/s +2s -3
= F_1(x,y,z）+（2s+3)(s-3)/s
≧0, （s=x+y+z≧3)