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a(1-a)≤{[(1-a)+a]/2}^2=1/4b(1-b)≤{[(1-b)+b]/2}^2=1/4c(1-c)≤{[(1-c)+c]/2}^2=1/4abc﹙1-a﹚﹙1-b﹚﹙1-c﹚≦﹙¼﹚³