美国初中数学

美国初中数学Chapter1.Variables,ExpressionsandIntegersPREREQUISITESKILLSQUIZ ReviewVocabularysumdifferenceproductquotientfactor PreparingforSuccessToprepareforsuccessinthischapter,testyourknowledgeoftheseconceptsandskills.Youmaywanttolookatthepagesreferredtoinblueforadditionalreview.VocabularyCopyandcompletethestatementusingareviewword.1.Inthemultiplicationequation12×5=60,12and5arecalledand60iscalledthe.2.Whenyoudivideonenumberbyanother,theresultiscalledthe.Findthesumordifference.3.7.2+13.7=4.2.41+34.6=5.10.5-7.3=6.27.1-18.6=Findtheproductorquotient.7.3.2×1.4=8.0.5×27=9.27.88÷8.2=10.11.9÷1.7=NOTETAKINGSTRATEGIESKEEPINGANOTEBOOKSomeusefulitemstoputinyournotebookincludethefollowing. NoteWorthyYouwillfindanotetakingstrategyatthebeginningofeachchapter.Lookforadditionalnotetakingandstudystrategiesthroughoutthechapter. •assignments•formulas•rulesandproperties•vocabulary•symbols•worked-outexamplesWhenyoucopyexamplesintoyournotebook,youmayfindithelpfultodrawadiagram.Includecommentsthatmakethesolutionprocessclear.Forexample,adiagramcanhelpyoutoorderthenumbers3.2,3.09,3,3.15,3.12,and3.02fromleasttogreatest.Drawanumberlineandgraphthenumbers:Writethenumbersintheorderinwhichtheyappearfromlefttoright:3,3.02,3.09,3.12,3.15,3.2.InLesson1.8,youmaywanttoincludeadiagramofacoordinateplaneinyournotebook.Lesson1.1ExpressionsandVariables Vocabularynumericalexpressionvariablevariableexpressionevaluateverbalmodel Before:Youevaluatednumericalexpressions.Now:You’llevaluateandwritevariableexpressions.Why?Soyoucanfindtheamountleftonagiftcard,asinEx.39.BlueWhalesDuringitssummerfeedingseason,abluewhaleeatsabout4tonsoffoodeveryday.Tofindabouthowmanytonsoffoodabluewhaleeatsinagivennumberofdays,youcanmultiplythenumberofdaysby4,asshowninthetable.    Anumericalexpressionconsistsofnumbersandoperations.Inthetable,theexpression4p10isanumericalexpression.Itcanalsobewrittenas4×10or4(10).Avariableisaletterusedtorepresentoneormorenumbers.Avariableexpressionconsistsofnumbers,variables,andoperations.Onewayyoucanuseavariableexpressionistogeneralizeapattern,asinthetable.Thevariableexpression4٠drepresentstheamountoffoodabluewhalecaneatinddays.Youcanalsowrite4٠das4d.Toevaluateavariableexpression,substituteanumberforeachvariableandevaluatetheresultingnumericalexpression.StudyStrategyExample1.EvaluatingaVariableExpression Whenyouwriteavariableexpressioninvolvingmultiplication,avoidusingthesymbol×.Itmaybeconfusedwiththevariablex. Evaluatetheexpression4×dwhend=120tofindabouthowmanytonsoffoodabluewhaleeatsinafeedingseasonof120days.Solution4٠d=4٠120Substitute120ford.=480Multiply.AnswerAbluewhaleeatsabout480tonsoffoodin120days.Example2.EvaluatingExpressionswithTwoVariablesEvaluatetheexpressionwhenx=10andy=4.a.x+y=10+4Substitute10forxand4fory.=14Add.b.xy=10(4)Substitute10forxand4fory.=40Multiply.CheckpointEvaluatetheexpressionwhenx=6andy=12.1.y+82.9-x3.y-x4.xyWritingVariableExpressionsYoucansolveareal-worldproblembycreatingaverbalmodelandusingittowriteavariableexpression.Averbalmodeldescribesaproblemusingwordsaslabelsandusingmathsymbolstorelatethewords.Thetableshowscommonwordsandphrasesthatindicatemathematicaloperations. WatchOut CommonWordsandPhrasesthatIndicateOperationsAdditionSubtractionMultiplicationDivision Orderisimportantinsubtractionanddivisionexpressions.“Thedifferenceofanumberand7”meansn-7,not7-n.“Thequotientofanumberand5”meansn/5,not5/n. PlusminustimesdividedbythesumofthedifferenceoftheproductofdividedintoincreasedbydecreasedbymultipliedbythequotientoftotalfewerthanofmorethanlessthanaddedtosubtractedfromExample3.WritingaVariableExpressionBaseballYouplantodividethe120playersinabaseballleagueintoteamswiththesamenumberofplayers.Useaverbalmodeltowriteavariableexpressionforthenumberofteamsifyouknowthenumberofplayersoneachteam.Solution ReadingAlgebra Letprepresentthenumberofplayersoneachteam.Theworddivideindicatesdivision. Whenyouwriteavariableexpressioninvolvingdivision,useafractionbarinsteadofthedivisionsymbol÷.Forexample,write“thequotientofnand12asn/12. inleague=120/p6VocabularyCheck1.Identifythevariableintheexpression21+d.2.Compareandcontrasttheexpressions2+xand2+3. SkillCheck Evaluatetheexpressionwhenx=4.3.10-x4.x+75.2x6.32/xEvaluatetheexpressionwhenm5andn6.7.n/2           8.m+n9.n-m10.Mn GuidedProblemSolving 11.AstronautsIn2002,astronautsCarlWalzandDanBurschspent196daysinorbit.Howmanysunrisesdidtheysee? 1 AnastronautinorbitcirclesEarthevery90minutesandsees16sunriseseachday.Letdbethenumberofdaysanastronautisinorbit.Writeavariableexpressionforthenumberofsunrisesseeninddays. 2 IdentifythevalueofdforWalz’sandBursch’s2002spaceflight. 3 FindthenumberofsunrisesWalzandBurschsaw.PracticeandProblemSolving   Evaluatetheexpressionwhenx=6.12.x+313.15-x14.2x15.x/3   16.20x17.24/x18.30-x19.15+xEvaluatetheexpressionwhena=4,b=2,andc=16. OnlineResources 20.a+b21.c-a22.ab23.a/b   24.bc25.c/a26.a–b27.c/b28.b+c29.c-b30.ac31.a+cWriteavariableexpressiontorepresentthephrase.32.Theproductof72and33.Thedifferenceofanumberanumberand134.13morethananumber35.Thesumofanumberand9.436.Thequotientofanumberand337.Anumberdividedby41 38.ErrorAnalysisDescribeandcorrecttheerrorinwritingavariableexpressionforthedifferenceofanumberand31. 39.GiftCardYoucanevaluatetheexpression50-dtofindtheamountyouhaveleftona$50giftcardafteryouhavespentddollars.Findtheamountleftafteryouhavespent$18.40.MusicCompetitionThedoublebargraphshowsthreestudents’scoresinamusiccompetition.Astudents’finalscoreisthesumofthepointsfortechniquetandforinterpretationi.a.Writeavariableexpressionforastudent’sfinalscore.b.Findeachstudent’sfinalscore.c.InterpretYouearn35pointsfortechnique.AtleasthowmanypointsmustyouearnforinterpretationtohaveahigherscorethanstudentsA,B,andC?Evaluatetheexpressionwhena=2.5,b=15,andc=3.5.41.a+b42.b-c43.bc44.a+c45.b/a     46.c–a47.c/a     48.acWriteavariableexpressiontorepresentthephrase.   49.Thenumberofinchesinxfeet50.Thenumberofpoundsinyounces   51.DVDRentalsYoubelongtoanonlineDVDrentalservice.Youryearlyrentalbudgetis$200.Eachrentalcosts$4. a.Copyandcompletethetable.b.Writeavariableexpressionforthecostofrrentals.   c.Writeavariableexpressionfortheamountofyourbudgetleftafterrrentals.  d.WritingHowmanyDVDswillyoubeabletorentbeforethe$200isspent?Explainhowyoufoundyouranswer. 52.ExtendedProblemSolvingInfootball,eachfieldgoal(FG)isworth3points.Eachkickedpointaftertouchdown(PAT)isworth1point.Thetableshowscareertotalsforthreeleadingkickers. a.Letpbethenumberofpointsaftertouchdownthatakickerscored,andletfbethenumberoffieldgoals.Writeavariableexpressionforthetotalnumberofpoints.b.EvaluateFindthetotalnumberofpointsforeachkicker.c.CompareListtheplayersinorderfromleasttotalnumberofpointstogreatest.53.CriticalThinkingArethereanyvaluesofthevariableaforwhichtheexpressions2+aand2ahavethesamevalue?Explain.LogicalReasoningDescribethepatternshowninthetable.Thenwriteavariableexpressioninvolvingntocompletethetable.Inthetable,thethreedotsindicatethatthepatterncontinues.54.Costofitem(dollars)1.002.003.004.00...nCostwithtax(dollars)1.052.103.154.20...?  55. Costofitem(dollars)1.001.502.002.50..n.Costwithcoupon(dollars)0.501.001.502.00...?56.ChallengeTheplastictipsontheendsofashoelacearecalledaglets.Supposeasneakerfactoryproducesppairsofshoeseachhourandisinoperationforhhourseachday.Writeavariableexpressionforthenumberofsingleagletsthefactoryuseseachday.Evaluatetheexpressionwhenp=200andh=24.Explainwhatyouranswermeans.MixedReviewFindthesumordifference.57.3.2+4.758.5.1+6.859.7.3-2.160.9.9-5.4Findtheproductorquotient.61.8(13.2)62.12.5/563.24.32/3.264.(6.5)(4.3)65.Orderthedecimalsfromleasttogreatest:8.9,8.79,7.98,9.87,7.8,9.78. StandardizedTestPractice 66.MultipleChoiceWriteavariableexpressionforalengthoftimeinminutesifyouknowthenumbersofseconds.A.s+60B.s/60C.60sD.60/s67.MultipleChoiceEvaluatetheexpressionx-ywhenx=12.8andy=4.F.3.2G.8.8H.12.4I.13.2Lesson1.2PowersandExponents Vocabularypowerbaseexponent Before:Youmultipliedwholenumbersanddecimals.Now:You’llusepowerstodescriberepeatedmultiplication.Why?Soyoucanfindthetotalnumberofe-mailssent,asinEx.29.Apoweristheresultofarepeatedmultiplicationofthesamefactor.Forexample,thenumber125isapowerbecause125=5•5•5.Apowercanbewritteninaformthathastwoparts:anumbercalledthebaseandanumbercalledtheexponent.Theexponentshowsthenumberoftimesthebaseisusedasafactor.Thetableshowshowtoreadandwritepowers.Numbersraisedtothefirstpower,suchas121,areusuallywrittenwithouttheexponent.     NoteWorthy Example1.UsingExponentsWritetheproductusinganexponent. Writeadditionalexamplesofyourowninyournotebook.Foreachproduct,identifythebaseandtheexponent,thenwritetheproductusinganexponent. a.13•13•13•13=134Thebase13isusedasafactor4times.b.(0.2)(0.2)(0.2)=(0.2)3Thebase0.2isusedasafactor3times.c.n•n•n•n•n•n=n6Thebasenisusedasafactor6times.d.t•t•t•t•t=t5Thebasetisusedasafactor5times.CheckpointWritetheproductusinganexponent.1.10•10•102.(4.3)(4.3)3.x•x•x•x4.CriticalThinkingEvaluateeachpower:02,03,04.Useyourresultstowritearuleforthevalueof0raisedtoanynonzerowholenumberexponent.102Example2.EvaluatingPowerswithVariablesEvaluatetheexpressionx4whenx=0.5.x4=(0.5)4Substitute0.5forx.=(0.5)(0.5)(0.5)(0.5)Use0.5asafactor4times.=0.0625Multiply.CheckpointEvaluatetheexpressionwhenm=3.5.m26.m37.m48.m5   UsingFormulasAformuladescribesarelationshipbetweenquantities.Someformulasinvolvepowers.Forexample,youcanuseaformulatofindtheareaofasquareorthevolumeofacube.Areaismeasuredinsquareunits,suchassquarefeet(ft2)orsquarecentimeters(cm2).Volumeismeasuredincubicunits,suchascubicinches(in.3)orcubicmeters(m3).Example3Example2.UsingPowersinFormulas IceSculptureAnartistusesacube-shapedblockoficetomakeanicesculptureforacompetition.Findthevolumeoftheblockofice. SolutionUsetheformulaforthevolumeofacube. V=s3Writetheformula. =(20)3Substitute20fors.IntheRealWorldIceSculptureAcubicinchoficeweighsabout0.03pound.Iftheartistcarvesawayabout2000cubicinchesfromtheblockinExample3,abouthowmuchdoestheresultingsculptureweigh?Exercises =8000Evaluatepower.AnswerThevolumeoftheblockoficeis8000cubicinches.CheckpointFindtheareaofasquarewiththegivensidelength.9.9meters10.11inches11.1.5centimetersGuidedPractice VocabularyCheck 1.Identifythebaseandtheexponentintheexpression135.2.Howaretheexpressions34and43different? SkillCheck Writethepowerinwordsandasarepeatedmultiplication.Thenevaluatethepower.3.1224.(0.3)35.(1.2)36.54Evaluatetheexpressionwhenk=6.7.k28.k39.k410.k511.GiftBoxAgiftboxhastheshapeofacubewithanedgelengthof14inches.Findthevolumeofthebox. 12.ErrorAnalysisDescribeandcorrecttheerrorinwriting23asarepeatedmultiplication.PracticeandProblemSolving   Writetheproductusinganexponent.13.32•3214.11•11•1115.6•6•6•6•616.2•2•2•2 17.(5.6)(5.6)(5.6)18.(1.7)(1.7)19.z•z•z20.n•n•n•nWritethepowerinwordsandasarepeatedmultiplication.Thenevaluatethepower.     OnlineResources 21.8322.2523.10624.12325.9326.4427.(0.2)228.(0.6)429.ExtendedProblemSolvingYousendane-mailto4friends.Eachfriendsendsthee-mailto4morefriends.Eachofthosefriendssendsitto4friends,andsoon.a.Copyandcompletethetable.b.CalculateFindthenumberofe-mailssentatstage9.c.EstimateEstimatethestageatwhichmorethan1,000,000e-mailswillbesent.Useacalculatortocheckyourestimate.  Evaluatetheexpressionwhenn7andwhenn0.4.30.n231.n332.n433.n534.WritingThesquareofanumberisthesecondpowerofthenumber.Thecubeofanumberisthethirdpowerofthenumber.Explainwhythesenamesarereasonable.35.CriticalThinkingExplainwhy1raisedtoanypowerisequalto1.36.AquariumsAnaquariumhasasquarebasewithasidelengthof15inches.Youfilltheaquariumwithwatertoaheightof15inches.a.Findthevolumeofthewaterintheaquarium.b.Acubicinchofwaterweighsapproximately0.036pound.Findtheapproximateweightofthewaterintheaquarium. 37.PatternsThetableshowssumsofoddnumbers.a.Copyandcompletethetable.Identifyanypatternthatyousee.b.Writeavariableexpressionforthesumofthefirstnoddnumbers.  c.Useyourexpressionfrompart(b)tofindthesumofthefirst100oddnumbers. 38.ChallengeFindvaluesofx,y,andzsothateachoftheexpressionsx2,y3,andz6hasavalueof64.MixedReviewFindtheproductorquotient.39.(2.5)(7.1)40.(2.3)(8.4)41.1.2÷2.442.5.2÷1.25 43.OlympicsThebargraphshowsthenumberofgoldmedalswonbythefourcountrieswiththemostgoldmedalsinthe2000OlympicSummerGames.Howmanygoldmedalsdidthefourcountrieswininall?  Evaluatetheexpressionwhenx=15.44.x+445.200-x46.x-1147.3xStandardizedTestPractice 48.MultipleChoiceWhichexpressionhasavalueof81?A.43B.34C.28D.273 49.ShortResponseCompareeachnumberinthetoprowofthetablewiththenumberbelowit.Describeanypatternyousee.Completethetablewithavariableexpressioninvolvingn. 1234...n182764...?StudentReference ReviewthistopicinpreparationforsolvingproblemsinLesson1.3.Forareviewofproblemsolvingstrategies. AProblemSolvingPlanYoucanusethefollowing4-stepplantosolveaproblem.   1.ReadandUnderstandReadtheproblemcarefully.Identifythequestionandanyimportantinformation.2.MakeaPlanDecideonaproblemsolvingstrategy.3.SolvetheProblemUsetheproblemsolvingstrategytoanswerthequestion.4.LookBackCheckthatyouranswerisreasonable.ReadingandPlanningExampleYouplantoship5bookstoafriend.Thetableshowsthemassesofthebooks.Isitpossibletoshipthebooksin2boxes,eachwithamassof6kilogramsorless?Explain.BookABCDEMass(kg)1.42.13.81.92.5ReadandUnderstandWhatdoyouknow?Themassofeachboxmustbe6kilogramsorless.Thetablegivesthemassofeachbook.Whatdoyouwanttofindout?Isitpossibletoputthebooksin2boxessothateachboxhasamassof6kilogramsorless?MakeaPlanHowcanyourelatewhatyouknowtowhatyouwanttofindout?Checkthatthetotalmassofthebooksdoesn’texceed12kilograms.Ifitdoes,youcan’tdividethebooksasyouwant.Usethestrategyguess,check,andrevisetochoosebooksforeachbox.SolvingandLookingBackTosolvetheproblemfrompage14aboutshippingbooks,carryouttheplan.Thenchecktheanswer.SolvetheProblemThetotalmassofthebooksis1.4+2.1+3.8+1.9+2.5=11.7kg,soitmaybepossibletoshipthebooksasyouwant. Nowusethestrategyguess,check,andrevise.Putthe3lightestbooksinoneboxandthe2heaviestintheother.Themassofthesecondboxismorethan6kg.  TryswitchingbooksBandE.Themassofeachboxislessthan6kg. AnswerItispossibletoshipthebooksin2boxes,eachwithamassof6kgorless.PutbooksA,D,andEinoneboxandbooksCandBintheother.LookBackItmakessensethattheboxwith3bookscontainsthe2lightestbooksandtheboxwith2bookscontainstheheaviestbook.So,theanswerisreasonable.CheckpointTestyourknowledgeoftheproblemsolvingplanbysolvingtheseproblems. 1.PoolSchedulesAcommunitypooloffers3swimsessionseachSaturdaymorning.Eachsessionlasts35minutes,with10minutesbetweensessions.Thefinalsessionendsat11:05A.M.Atwhattimedoesthefirstsessionbegin?2.TheaterSeatingThecentersectionofatheaterhas10rows.Thereare41seatsinrow10,38seatsinrow9,35seatsinrow8,andsoon.Howmanyseatsareinrow1?3.MovieMarathonYouhaveinvitedfriendsovertowatchmovies.Youhaverented4movies:oneaction,onesciencefiction,onecomedy,andoneanimated.Inhowmanydifferentorderscanyouwatchthemovies?Lesson1.3OrderofOperations Vocabularyorderofoperations, Before：Youperformedbasicoperations.Nowadays：You’lluseorderofoperationstoevaluateexpressions.Why？Soyoucanfindtheheightofaboojum,asinEx.28.       FlowerFlagThereareabout2000plantsineachofthe50starsofthisflowerflag.Thereareabout64,100plantsineachofthe7shortstripesand106,700plantsineachofthe6longstripes.Theblueregioncontainsabout198,900plants.Youcanapproximatethetotalnumberofplantsbyevaluatingtheexpression50•2000+7•64,100+6•106,700+198,900.Toevaluateexpressionsinvolvingmorethanoneoperation,mathematicianshaveagreedonasetofrulescalledtheorderofoperations.NoteWorthyOrderofOperations1.Evaluateexpressionsinsidegroupingsymbols. Youshouldincludematerialthatappearsonanotebookliketheoneshowninyourownnotebook. 2.Evaluatepowers.3.Multiplyanddividefromlefttoright.4.Addandsubtractfromlefttoright.Example1.UsingOrderofOperationsToapproximatethetotalnumberofplantsintheflowerflagdescribedabove,usetheorderofoperationstoevaluatetheexpression50•2000+7•64,100+6•106,700+198,900Writeexpression.=100,000+448,700+640,200+198,900Multiply.=1,387,800Add.AnswerThereareapproximately1,387,800plantsintheflowerflag.GroupingSymbolsParentheses(),brackets[],andfractionbarsarecommongroupingsymbols.Groupingsymbolsindicateoperationsthatshouldbeperformedfirst.Forexample,comparetheexpressions3•2+5and3(2+5).Toevaluate3•2+5,youmultiplyfirst,thenadd.Toevaluate3(2+5),youaddfirst,thenmultiply.Example2.UsingGroupingSymbolsEvaluatetheexpression.a.8(17-2.3)=8(14.7)Subtractwithinparentheses.=117.6Multiply. WatchOut b.=(14+6)÷(12-7)Rewritefractionasdivision.Whengroupingsymbolsappearinsideothergroupingsymbols,asinpart(c)ofExample2,workfromtheinnermostgroupingsymbolsout. =20÷5Evaluatewithinparentheses.=4Divide.c.5•[36-(13+9)]=5•[36-22]Addwithinparentheses.=5•14Subtractwithinbrackets.=70Multiply.CheckpointEvaluatetheexpression.1.28-63÷72.52+12.5•43.9•6+27÷34.10(1.5+0.6)5.6.72÷[(11-7)•2]EExample3.EvaluatingVariableExpressions StudyStrategy Evaluatetheexpressionwhenx=2andy=5.a.4(x+y)=4(2+5)Substitute2forxand5fory.YoucanusethefirstlettersofthewordsofthesentencePleaseExcuseMyDearAuntSallytohelpyouremembertheorderofoperations.PparenthesesEexponents =4(7)Addwithinparentheses.=28Multiply.b.3(x+y)2=3(2+5)2Substitute2forxand5fory.=3(7)2Addwithinparentheses.=3(49)Evaluatepower. M/DmultiplicationanddivisionA/Sadditionandsubtraction 147Multiply.CheckpointEvaluatetheexpressionwhenx=4andy=2.7.1.2(x+3)8.1.2x+39.3x-2y10.0.5[y-(x-2)]11.x2–y12.2(x-y)2EExample4.UsingaProblemSolvingPlanSewingYoubuyapatternandenoughmaterialtomaketwopillows.Thepatterncosts$5.Eachpillowrequires$3.95worthoffabricandabuttonthatcosts$.75.Findthetotalcost.SolutionReadandUnderstandYoubuyonepatternplusfabricandbuttonsfortwopillows.Youareaskedtofindthetotalcost.MakeaPlanWriteaverbalmodel.SolvetheProblemWriteandevaluateanexpression.Totalcost=5+2(3.95+0.75)Substitutevaluesintoverbalmodel.=5+2(4.70)Addwithinparentheses.=5+9.40Multiply.=14.40Add.AnswerThetotalcostis$14.40.LookBackUseestimationtocheckthattheanswerisreasonable.Thecostofmaterialsforeachpillowisabout$4+$1=$5.Thetotalcostisabout$5+2($5)=$15.Theanswerisreasonable. 1.3 ExercisesGuidedPractice  VocabularyCheck1.Givethreeexamplesofgroupingsymbols.2.Describeinorderthestepsyouwouldtaketoevaluatetheexpression12(x-3)2whenx=5.SkillCheckEvaluatetheexpression.3.15-3•44.48÷6+25.3•8+5•46.7.17-(32-2)8.4[15-(2+5)] 9.TwinConventionThetableshowsthenumbersofsetsoftwins,triplets,quadruplets,andquintupletsregisteredatatwinconvention.Writeandevaluateanexpressionforthetotalnumberofpeoplewhoregisteredattheconvention.PracticeandProblemSolving   Evaluatetheexpression.10.47.7-12•311.11•7-9•512.14÷7+36÷4   13.5.8(3)+3(1.1)14.3615.9.8216.5(21-32)17.7[2.5+3(12-7)]18.84÷[(18-16)•3]Evaluatetheexpressionwhenx=3,y=4,andz=5. OnlineResources 19.0.25y+x20.0.25(y+x)21.4(z-x)22.23.x+24.424.7z-x225.x+2[z-(y-1)]26.(x+y)2-3.627.y+(z-1)228.PlantsAboojumisaveryslow-growingcactus.Onefifty-year-oldboojumis1.5meterstallandhasbeengrowingabout0.03metereachyear.Assumethegrowthpatterncontinues.a.Writeanexpressionfortheheightinmetersoftheboojumyyearsfromnow.b.ApplyHowtallwilltheboojumbein50years?29.CraftFairYourschoolissettinguparowof5tablesforacraftfair.Eachtableis72incheslong.Thespacebetweeneachpairofneighboringtablesmustbe48inches.Writeandevaluateanexpressiontofindthelengthofthespaceneededforthetablesfromthebeginningofthefirsttabletotheendofthelasttable.30.BasketballInbasketball,playersscorepointsbymakingfreethrowsworth1pointeach,fieldgoalsworth2pointseach,andfieldgoalsworth3pointseach.Aplayerscores4freethrows,7two-pointfieldgoals,and2three-pointfieldgoals.Writeandevaluateanexpressionforthetotalnumberofpointstheplayerscores.31.MoviesYoubuy4videotapesfor$14.99eachand3DVDsfor$19.99each.Findthetotalcostofthemovies.Evaluatetheexpressionwhenx=4andy=3.26.5y232.5x22y3