It's hard when a best friend isn't around—maybe because you move to a different school or a different class. You may feel lonely at break (课间) or lunchtime. You want to have new friends，but how do you make them?

    Start by looking around your classroom. Think about which kids you'd like to play with at break. Say hi to them，smile，and be friendly. Ask them to enjoy something or talk with them about something they may be interested in. Invite someone to play with you or ask “Do you want to sit here？” in the lunchroom. When you're at break，walk to kids you want to play with，and say “Hi，can I play，too？” or just join in.

    If you are feeling shy (害羞)，ask your teacher to help you make new friends. Teachers are usually good at matching up friends. The best way to make friends is to be a friend. Be kind，be friendly，say nice things and help others—soon you'll have one，or two，or even more new friends.

①函数f（x）=x+ $\frac{9}{x}$ 的最小值为6；

②不等式 $\frac{2x}{x+1}$ ＜1的解集是{x|﹣1＜x＜1}；

③若a＞b＞﹣1，则 $\frac{a}{1+a}$ ＞ $\frac{b}{1+b}$ ；

④若a＞b，c＞d，则ac＞bd．

所有正确命题的序号是____．

“今夫封建者，继世而理；继世而理者，上果贤乎，下果不肖乎？则生人之理乱未可知也。将欲利其社稷以一其人之视听，则又有世大夫世食禄邑，以尽其封略，圣贤生于其时，亦无以立于天下，封建者为之也。岂圣人之制使至于是乎？”据以上材料判断，作者认同的是（    ）