中考必做的36道压轴题及变式训练

O

mxmxm

AB

l

ABl

l

ABx

y

A（0，－2）．x

mm

b

A

A（2，－2）l

A

B

ykxb

b

b

yx

x

＝1

x

x

x

l

x

l

l

xyx

xmm

myx

x

yaxmaxmam

aa

mxC

xAByDABC

aABCABDmyaxmaxmaxamaxamam

a

amaaamamaaxamaxamam

a

mx

yaxmaxmax

m

C

m

y

axmaxm

xmxm

ABABC

a

a

x

yamam

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am

am

amam

amam

m

m

m

(

m

m

C

nn

(

m

m

）.

n

n

n

n

n

nn

M

M

AOC

COB

AOCCOBACO=ACBACOOCB=CBOOCBABCABCAB

MBCM

AB

A

B

PAB

AB

P

AB

CPDAB

D

ab

Pmm

PDPD

PB

PCPDB

m

m

,

+4b

,

b

b

AB

EE

PC

m,

m

m

m

m

m,m

m

m

m

m

m

m

m

m

.

或m

m

或

DB

DFPCBGPCFG

DF

mm

DF

m

DF

m

m

m m m

m

m m

m

yxbx

P

bx

y

PmyPmyPmy

m

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m

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x

BA

yC

BCMxM

MNyBCN

MNMNPx

BCCBPQCBPQ

ABN

P

B BC

mxBCm

m

BC

BC

b

b

解得：

所以抛物线的解析式为：

Mx

Nx

MN(

(

MN

MN

B

ABAB

N

QPBC

QP

P

m

F

MNMA

ANB

B

m

m

N

N

NFNB

NM

P

PAPB

M

m

m

m

mm

N

N

N

F

FCNB

C

eq

\o\ac(△,Rt)

FCNFCNCNBCB

FC

NFNB

AFBFFPABPFPFAPBF

PF

NFNBNFBFPABPFPFAPBF

PF

NB

MANBAMFBNFMAFNFBMAFNBFMAFNBFMABNBAFBAFABFABMAFFBAMAFMFA PF

PF

F

FG

G

RtPFG

PG PF

FG

，∴POPGGO

P

b

PF

b

b

b

PF

M

b

ABCO

MN

CDxllONl

MN

k

MN

l

MNN M

ll

bb

ON

y

ON

b

MxyNxyMN

ON

ENE

lPF

EF

ONEF

ONlON

ONl

M

MHNP

NP

HMN

ykxykx

MN

MN

ykx

x

k

MN

MN

NP

l

QM

MSl

S

MS

NQ

(

)

MS

NQMN

MNlMN M F

N

ll

x

AB

y

C

AC

P

xPAPCOP

MMACH

M

yCHM

AOC

C

AM

M

M

xy

a

a

OPx

PCPAx

eq

\o\ac(△,R)

POC

CHMAOCMCHCAO

HCMCHCAOCMx

M

xx

M

HCMCHCAOMCP

CMyx

P

xx

M

,

xDD

DEAC

E

DE

COADEAOACEADADEAOC

DE

ADD

D

D

DMACM

DM

x

x

x

xx

x

,

M

M

M

b

b

b

=

x

yC

AB

OC

E

A

x

B

E

E

l

BC

AC

D

AE

eq

\o\ac(△,m)

ADES

S

m

meq

\o\ac(△,CE)

CDEEBC

y=

y=

x

x=

y=OC=.

ABC

BCy=

x

ACy=xAEmE

m

l

BC

m

=

D

=

D

m

m|=

|=

··

m

m

CDEeq

\o\ac(△,S)

ACEeq

\o\ac(△,－S)

CDEeq

\o\ac(△,S)

ACEeq

\o\ac(△,－S)

ADE=

m

－

m

m)=

m+3m=

m+ ，

m=

CDE

EOFBC

FOB=OC=OF=

EBC

=

第6题

A

B

C

ABeq

\o\ac(△,P)

PAB

AB

ACEACACAEOAB

eq

\o\ac(△,F)

OE

bb

0=9a+3ba=解得b= ２ ５∴解析式为ｙ＝

ｘ－

ｘ＋３ ２令ｘ＝０时，ｙ＝３∴点坐标为

PEa

Paa

aa

PBA

xD

PB

xEF PED、△BAD

PEa，则

DEaAB

AD

Pa

a

a

B

PP

CAOOEFOAFEFOEAOEOF

OE

OEE

AC

,

(

)

、

、

△

M

△

△

M

C

C

Ａ Ｏ Ｂ

ＣＤ

h

Ｄ

，

=-4

E

DF

F

R△

R△

R△CFD

OMBC

AC

MＭ

△

△∽

△

AM