已知a²﹣3a+1=0，则（a²﹣$\frac{1}{a^2}$）（a﹣$\frac{1}{a}$）=____ ．

    Welcome to a day of my life in 2037．I am Li Ming．I work in an office．I don't need to work in the afternoon．At 8：00 in the morning．my robot servant Smart will wake me up．He will cook me a nice breakfast and then drive me to my office．After 10 minutes, I arrive my office．Then a big screen will show me what to do the day．At lunch time，I will have my lunch with some of my good friends in a restaurant．The robots there will make all of the dishes．They are delicious!

    There will be a concert in the center(音乐会)music hall at 14：00．The singers are from all over the world．I will go there with my friends to enjoy many kinds of music．I think we will have a good time．

    At 17：00，we will take the spaceship to the moon．It will take us about half all hour to get there．We will enjoy the hot spring(温泉)on the moon and watch Earth TV News on the dome(穹顶)screen over our head．Then we will go back to the earth at 20：00．About half an hour later，I arrive at my house and say goodbye to my friends．After a shower and a glass of milk，I will go to bed and have a nice dream．

Information Card

法律保障公民的通信自由和秘密。下列不属于侵犯公民通信自由和通信秘密的行为是 （   ）

有一包粉末，可能由氯化银、碳酸钠、氢氧化镁、氯化钡、硫酸钠和硝酸钾中的某几种组成．为了鉴定其成分，实验如下：

①将少量粉末放入足量水中，搅拌、静置、过滤、得白色沉淀和无色滤液．

②向所得沉淀中加入足量稀硝酸，沉淀全部溶解，但无气体产生．

③向滤液中滴加硝酸银溶液，有白色沉淀生成，加入足量稀硝酸，沉淀不溶解．

试根据以上现象推断该白色粉末中一定含有____；一定没有____；可能含有____．