题目

设全集为实数集R，， ⑴当时，求； ⑵ 若，求实数的取值范围。   答案：解：（1）∵A={x|  ≤x≤3}， 当a=﹣4时，B={x|﹣2＜x＜2}，  ∴A∩B={x|  ≤x＜2}， A∪B={x|﹣2＜x≤3}． （2）CRA={x|x＜ -2或x＞3}， 当（CRA）∩B=B时，BCRA， ①当B=，即a≥0时，满足BCRA； ②当B≠，即a＜0时，B={x|﹣＜x＜}， 要使BCRA，需≤，解得﹣≤a＜0． 综上可得，实数a的取值范围是a≥﹣． It is often said that eyes can speak. Do you have such kind of 11 ? In a bus you may look at a stranger, but not too, 12. If he notices that he is being looked at, he may 13 uncomfortable. It is the same in daily life. When you are looked at for several more times, you will look 14 up and down in order to 15 if there is anything wrong with you. If 16 goes wrong, you will feel angry with the person who is looking at you. 17 can speak, right? Looking too long at someone may seem to be impolite. But sometimes things are 18. If you wish to draw someone's 19 , you may look at him or her for more than ten seconds. For lovers, they enjoy looking at each other longer to show the love that words cannot 20 . Clearly, eye communication should be done according to the relationship between the two people and the certain situation.( ) 1. A. future B. fear C. experience D. exercise( ) 2. A. late B. long C. low D. loud( ) 3. A. feel B. smell C. sound D. taste( ) 4. A. itself B. himself C. myself D. yourself( ) 5. A. see B. guess C. hear D. expect( ) 6. A. something B. nothing C. everything D. anything( ) 7. A. Ears B. Eyes C. Mouth D. Nose( )18. A. different B. difficult C. tiring D. boring( ) 9. A. direction B. lesson C. attention D. trouble( )10. A. write B. print C. read D. Express