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(120150)(10,4,40)1.(a-3)x2+(b+1)x+c=0x,A.aB.aC.ab-1D.ab-1c2.xx2+x-a=02,A.-3B.-2C.3D.63.OABCD,OA=OB=OC=OD,ABCDA.B.C.D.4.a,b,c,P(a,c),xax2+bx+c=0A.B.C.D.5.,O,OACB,C(6,0),A2,BA.(2,3)B.(3,2)C.(2,-3)D.(3,-2)6.,,?ABCDAB=BC,BAD=90ACBD,AC=BD;OA=OD,BC=CD;BOC=90ABD=DCA.A.1B.2C.3D.47.20154.4,,.20179.7,20162017x,A.4.4(1+x)=9.7B.4.4(1+2x)=9.7C.4.4(1+x)2=9.7D.4.4(1+x)+4.4(1+x)2=9.78.,,,,:,,A.0.6B.0.5C.0.45D.0.49.(1~6),,;,,A.B.C.D.10.,ABCD,FAD,EBC,EF,DBCG.4AFG=60GE=2BG,EF3A.1B.3C.2D.23(4,5,20)11.x2-6x=7(x+m)2=b,m=-3,b=16.12.,,,(),,.1313.,(a,b),a2-2b+3.(x,-2x),-1,x=-2.14.,ABCD,AB=5,AD=8,EAD,ABEBE,AA'ABCD,AE.52533(2,8,16)15.:(1)x2-2x-3=0;x1=3,x2=-1(2)2(x-3)2=x2-9.x1=3,x2=916.mx2+x-1=0,2m2+2m+2018.:mx2+x-1=0,m2+m-1=0,m2+m=1,2m2+2m+2018=2(m2+m)+2018=21+2018=2020.(2,8,16)17.ABCD,ACDAB,ACBDO,DEABE.(1):ABCD;(2)AC=8,BD=6,DE.:(1)ABCD,ADBC,DAC=BCA.ACDAB,DAC=BAC,BCA=BAC,AB=BC.ABCD,ABCD.(2)ABCD,AC=8,BD=6,AO=4,BO=3,ACBD,AB==5.????2+????22SABD=ABDE=ACBD,125DE=86,DE=.1224518.,OABCD,DEAC,CEBD,DE.:(1)OCED;(2)OE=BC.:(1)DEAC,CEBD,OCED.ABCD,ACBD.DOC=90OCED.(2)ABCD,BC=CD.OCED,OE=CD,OE=BC.(2,10,20)19.,30.,10,.5000,1.1,5000.(1)13,??(2),275?(=-):(1)30-(130000-100000)5000=24,(13-1)24-60.5=285().:24,285.(2)x,(x-1)[30-(x-10)0.5]-[(x-10)0.5]0.5=275,x1=10.5,x2=15,:10.515.20.,ABCDEF,:,,A,(ADB).,,A?::9,A3,A.39=13(12)21.,30m,24m,,480m2,,?:xm,(30-3x)m,(24-2x)m,(30-3x)(24-2x)=480,x2-22x+40=0,x1=2,x2=20,x=20,30-3x=-30,24-2x=-16,,.:2m.(12)22.,,,:,A,9,;:,,8,.,(,).(1),9;14(2),,8.:(2),:,12,,,8,2,P(8)=.212=16:8.16(14)23.(1)1,ABCD,AD=5,S?ABCD=15,AAEBC,E,AEABE,DCE',AEE'D,AEE'D(C)A.B.C.D.(2)2,(1)AEE'D,EE'F,EF=4,AEF,DE'F',AFF'D.:AFF'D;AFF'D.:(2):AD=5,S?ABCD=15,AE=3.EF=4,AF==5,AF=AD=5.????2+????2=32+42AFDF',AF=DF',AFF'D,AFF'D.AF',DF.RtDE'F,E'F=E'E-EF=5-4=1,DE'=3,DF=.12+32=10S?ABCD=15,SAFF'D=15,AF'=15,1210AF'=3.10AFF'D,3.1010