题目

如图所示,在平行六面体ABCD—A1B1C1D1中,E、F分别在B1B和D1D上,且BE=BB1,DF=DD1.(1)证明A、E、C1、F四点共面;(2)若,求x+y+z. 答案：(1)证明:因为所以A、E、C1、F四点共面.(2)解:因为所以x=-1,y=1,z=.所以x+y+z=.2．Joseph Banks was born in 1743，the only son of a wealthy land-owning family．From an early age，he was interested in natural history，and in particular，botany．In the early 1760's he chose to make this dream to the full．In 1766 he travelled to Newfoundland and Labrador to collect plants，animals and rocks．For him，joining Captain Cook's 1768 expedition to Tahiti was like a present-day scientist being given the chance of a trip to another planet，a chance to study new plants in unknown lands．They made collections and observations in South America，Tahiti and New Zealand before reaching Australia．His major landfalls on the eastern coast of Australia were at Botany Bay and at the Endeavor River．He thought collection of plants was grown so large that it was necessary that some extraordinary care should be taken of them in case they should destroy．The plant material collected and sorted on the voyage was huge，with the herbarium specimens（标本）about 1300 new species．After returning from this voyage，Banks travelled to Scotland，Wales，Holland and Iceland，collecting more and more curiosities．Among many other activities，without thinking running out of his money，he controlled the Royal Botanic Gardens，Kew and was a Trustee of the British Museum．Although Linneaus'suggestion of naming the new country of Australia"Banksia"was not accepted，Banks'name was bestowed（赠送）upon Australian plants and he made his mark upon Australian history in other ways，later he became the well-known authority （公认的权威）on matters relating to New South Wales．He had a great impact on the study of natural history in both Britain and Australia．He died in 1820．41．When Banks was youngBA．he was only fond of botany B．he travelled to many placesC．his family was not very rich D．he hadn't much dream about his future42．The underlined word"curiosities"（in Paragraph 4）refers toDA．money B．time*C．many kinds of animals          D．new species of plants43．Which of the following can be inferred from the passage？CA．Australian people loved Banks．B．Banks died at the age of 76．C．Banks'trips to many places laid foundation for his achievements in botany．D．Both Banks and Linneaus devoted their whole loves to investigating plants．