a.b.c为正实数.且a+b+c=1 (1/a-1)(1/b-1)(1/c-1) =[(1-a)/a]*[(1-b)/b]*[(1-c)/c] =[(b+c)/a]*[(a+c)/b]*[(a+b)/c] ≥[2√bc/a][2√ac/b][2√ab/c] =8abc/abc =8 得证
