1。为什么2除以（1/a+1/b)不大于根号ab2.若a>2,求证：loga(a+1)*loga(a-1)<1急求，谢谢
热心网友
(1/a + 1/b) =2* (1/ab)^(1/2) 取倒数 1/(1/a + 1/b) <=1/[2* (1/ab)^(1/2)] 整理 2/(1/a + 1/b) <= (ab)^(1/2)
热心网友
1)(a+b)/2=√ab---2/(a+b)=2ab/(a+b)=√(ab)---2/(1/a+1/b)=√(ab).2)log(a+1)+log(a-1)<[log(a+1)+log(a-1)]/2=log(a^2-1)/2