填空题设x=rcosθ，y=rsinθ，把极坐标系中的累次积分转化为直角坐标系中的累次积分可得I=______．

填空题=________.

填空题设则x2项的系数为________．

填空题设，且α，β，γ两两正交，则a=________，b=________．

填空题设总体X～N(a，2)，Y～N(b，2)，从总体X取得简单随机样本X1，X2，…，Xm，从总体Y独立地取得简单随机样本Y1，Y2，…，Yn记统计量=，则T服从分布及参数为______．

填空题设A，B为三阶相似矩阵，且｜2E+A｜=0，λ 1 =1，λ 2 =－1为B的两个特征值，则行列式｜A+2AB｜=________。

填空题若线性方程组有解，则常数a1，a2，a3，a4应满足条件______．

填空题[A]Hemphasbeencultivatedbymanyculturesforthousandsofyears.Itproducesfibrewhichcanbemadeintopaper,fuel,oils,textiles,food,andrope.Formanycenturies,itwasessentialtotheeconomiesofmanycountriesbecauseitwasusedtomaketheropesandcablesusedonsailingships;colonialexpansionandtheestablishmentofaworld-widetradingnetworkwouldnothavebeenpossiblewithouthemp.Nowadays,ships'cablesareusuallymadefrom'wireorsyntheticfibres,butscientistsarenowsuggestingthatthecultivationofhempshouldberevivedfortheproductionofpaperandpulp.Accordingtoitsproponents,fourtimesasmuchpapercanbeproducedfromlandusinghempratherthantress,andmanyenvironmentalistsbelievethatthelarge-scalecultivationofhempcouldreducethepressureonCanada'sforests.[B]MuchofCanada'sforestryproductiongoestowardsmakingpulpandpaper.AccordingtotheCanadianPulpandPaperAssociation,Canadasupplies34%oftheworld'swoodpulpand49%ofitsnewsprintpaper.Ifthesepaperproductscouldbeproducedinsomeotherway,Canadianforestscouldbepreserved.Recently,apossiblealternativewayofproducingpaperhasbeensuggestedbyagriculturalistsandenvironmentalists:aplantcalledhemp.[C]Inrecentyears,twomajormovementsforlegalizationhavebeengatheringstrength.OnegroupofactivistsbelievesthatALLcannabisshouldbelegal--boththehempplantandthemarijuanaplant--andthattheuseofthedragmarijuanashouldnotbeanoffense.Theyarguethatmarijuanaisnotdangerousoraddictive,andthatitisusedbylargenumbersofpeoplewhoarenotcriminalsbutproductivemembersofsociety.Theyalsopointoutthatmarijuanaislesstoxicthanalcoholortobacco.[D]However,thereisaproblem:hempisillegalinmanycountriesoftheworld.Thisplant,sousefulforfibre,rope,oil,fuelandtextiles,isaspeciesofcannabis,relatedtotheplantfromwhichmarijuanaisproduced.[E]Theotherlegalizationmovementisconcernedonlywiththehempplantusedtoproducefibre;thisgroupwantstomakeitlegaltocultivatetheplantandsellthefibreforpaperandpulpproduction.Thissecondgrouphashadamajortriumphrecently:in1997,Canadalegalizedthefarmingofhempforfibre.Forthefirsttimesince1938,hundredsoffarmersareplantingthiscrop,andsoonwecanexpecttoseepulpandpaperproducedfromthisnewsource.[F]Inthelate1930s,amovementtobanthedrugmarijuanabegantogatherforce,resultingintheeventualbanningofthecultivationnotonlyoftheplantusedtoproducethedrug,butalsoofthecommercialfibre-producinghempplant.AlthoughbothGeorgeWashingtonandThomasJeffersongrewhempinlargequantitiesontheirownland,anyAmericangrowingtheplanttodaywouldsoonfindhimselfinprison--despitethefactthatmarijuanacannotbeproducedfromthehempplant,sinceitcontainsalmostnoTHC(theactiveingredientinthedrug).[G]Everysecond,1hectareoftheworld'srainforestisdestroyed.That'sequivalenttotwofootballfields.AnareathesizeofNewYorkCityislosteveryday.Inayear,thataddsupto31millionhectares--morethanthelandareaofPoland.Thisalarmingrateofdestructionhasseriousconsequencesfortheenvironment;scientistsestimate,forexample,that137speciesofplant,insectoranimalbecomeextincteverydayduetologging.InBritishColumbia,where,since1990,thirteenrainforestvalleyshavebeenclear-cut,142speciesofsalmonhavealreadybecomeextinct,andthehabitatsofgrizzlybears,wolvesandmanyothercreaturesarethreatened.Logging,however,providesjobs,profits,taxesforthegovernmentandcheapproductsofallkindsforconsumers,sothegovernmentisreluctanttorestrictorcontrolit.

填空题交换积分次序∫ 0 2 dx∫ x2 x f(x，y)dy=_______．

填空题设二元函数z=xex+y+(x+1)ln(1+y)，则dz|(1,0)=______．

填空题已知某商品的需求函数为，成本函数为C=50+2Q，则产量为________时利润最大．