题目错了吧，a,b是大于0的吧否则a=-2,b=-2时就不成立啦！(ab+a+b+1)(ab+1)=(a+1)(b+1)(ab+1)a+1>=0b+1>=0ab>=0 时(a+1)(b+1)(ab+1)>=2根号a*2根号b*2根号ab=8ab
