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1、二项式定理典型例题--典型例题一例1在二项式的展开式中，前三项的系数成等差数列，求展开式中所有有理项．分析：本题是典型的特定项问题，涉及到前三项的系数及有理项，可以通过抓通项公式解决．解：二项式的展开式的通项公式为：前三项的得系数为：，由已知：，∴通项公式为为有理项，故是4的倍数，∴依次得到有理项为．说明：本题通过抓特定项满足的条件，利用通项公式求出了r的取值，得到了有理项．类似地，的展开式中有多少项是有理项？可以通过抓通项中r的取值，得到共有17页系数和为．典型例题四例4（1）求展开式中的系数；（2）求展开式中的常数项．分析：本题的两小题都不是二项式展开，但可以转化为二项式展开的
2、问题，（1）可以视为两个二项展开式相乘；（2）可以经过代数式变形转化为二项式．解：（1）展开式中的可以看成下列几种方式得到，然后合并同类项：ith.3,fillembankmentbeforebaseandcompletedtheinspectionandacceptanceofworks.4,beforetherequirementlevelelevationsignlayoutaccordingtothedrawing,everynailonthelevelofacertaindistance,elevationofforkliftpartsaccordingtothedesi
3、gnrequirementsset.5,accordingtothesiteconditionsdeterminetheroutesofearth-movingmachinery,vehicles,andpriorchecks,reinforceandwidenifnecessaryandotherpreparatorywork.(B)constructionprocessesandmethods;1,process:beforefilling,andstatisticstotheexistingbuildingsandtrees,thesoilonthecaveoronthesu
4、rfaceofroots,trashandotherdebristobecleared.2,havethesoilinspectionwork.Speciesoffill,size,checkthereisnodebris,andsoilmoisturecontentcontrolwithinthedesignrange.Tier3,fillcasting:eachlayerthicknessaccordingtosoil,densitytodeterminerequirementsandequipmentperformance.4,asneededwhenrolling,whee
5、l(RAM)tracklappingeachother,preventleaksRAMleakage.Aspectishigh,fillingsegments.Eachlayerintoslope-shapedseams,groundtrackaboutoverlapping0.5-1.0M,islessthanthedistancefromtheupperandlowerjoints1M.5,filloutthebasesurface,wewilldotheedgecompactionqualityassurancework.Aftertheearth-moving,doesno
6、trequiretrimmingoftheslopewouldbepreferabletofillingedgefill0.5mwidecalledsloperidesonandshoot,widefilling0.2m.6,inmachineryconstructionnotrollingthefillingposition,manualbladefilledwithfrog-typerammingmachineordieselhierarchicaldynamiccompaction-compacting.9,rainduringconstruction:(1)intherai
7、nduringembankmentconstruction,wewillbecompletedassoonaspossibleacontinuous;facedonotseektoolarge,hierarchicalsegment-by-filmbasis,importantorspecialbackfill,ascompletedbytherain.(2)intherainatthetimeofconstruction,checkalltherain用展开式中的常
