1/2a+1/2b+1/2c=1/4a+1/4b+1/4a+1/4c+1/4b+1/4c=(a+b)/4ab+(a+c)/4ac+(b+c)/4bc又因为(a+b)/4ab-1/(a+b)=(a-b)^2/(4ab(a+b))>=0故(a+b)/4ab>=1/(a+b)同样的有(a+c)/4ac>=1/(a+c)(b+c)/4bc>=1/(b+c) 所以(a+b)/4ab+(a...