因式分（1）13-3a2；（2）9（x+y）2-4（x-y）2；（3）（x+y） 发布时间：2017-05-11 12:42 │ 来源：www.tikuol.com 题型：解答题 问题： 因式分（1）13-3a2； （2）9（x+y）2-4（x-y）2；（3）（x+y）2-4（x+y-1）； （4）-x2y+2xy2-y3．
题型：解答题 甲、乙、丙三人要装订语文和数学课本。装订语文课本的工作量比装订数学课本的工作量多1/4，甲、乙、丙三人单独完成数学课本的装订各需20天、24天和30天。为了共同完成这两项任务，先安排甲装订数学课本，乙、丙一起装订语文课本；经过几天后，又调丙去帮甲装订数学课本。最后两种课本的装订任务同时完成，那么乙、丙二人合作了（）天。A．12B．15C．17D．18 查看答案
题型：解答题 Artificial flowers are used for scientific as Well as for decorative purposes. They are made from (51) of materials, such as wax and glass, so skillfully that they can scarcely be (52) from natural flowers. In making such models, painstaking skill and artistry are called for, (53) thorough knowledge of plant structure. The (54) of glass flowers in the Botanical Museum of Harvard University is the most famous in North America and is widely known (55) the scientific world. (56) , there are several thousand models in colored glass, the work of two artist naturalists, Leopold Blalschka and his son Rudolph. The intention was to have the collection (57) at least one member of each flower family native to the United States. (58) it was never completed, it contains more than seven hundred species representing 164 families of flowering plants. (59) detail of these is accurately reproduced in color and structure. The models are (60) n locked cases as they are too valuable and fragile for classroom use.A．concentrationB．gatheringC．collectionD．assembly 查看答案
题型：解答题 不停气动火作业应符合下列哪些规定。（）A、对新、旧钢管连接动火作业时，应先采取措施使新旧管道电位平衡；B、用燃气浓度检测器对现场的燃气浓度进行检测，当确认操作环境不会发生燃气爆炸时，方可带气动火作业。C、带气动火作业时，管道内必须保持正压，其压力宜控制在300Pa∽800Pa，应有专人监控压力；D、动火作业引燃的火焰，必须有可靠、有效的方法随时将其扑灭。 查看答案