1.有点委琐哈~若a>b,ab>ad+bc ,bc若a=b,ab>ad+bc ,ad+ac,ad若aad+bc ,ad2.还是有点觉得不对劲阿~2b+ab+a=30(a>0,b>0) => 2/b+1/a+1=30/(ab) 2/b+1/a >= 2(2/(ab))^(1/2)=(8/(ab))^(1/2)=> (30/(ab)-1)^2 >= 8/(ab)解...