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#$#%&
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)67
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-7
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Mbdbd ''( =
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>
⇔ '
'
'
<=>B&J2M
l_
_
+=++ '''
J2M



+=+
−≥
⇔

=−
−≥
⇔ _
h

_h
''
''
'
<=>C&J2M
7_b_dbd
_
''''' =++−
(.f2MKM
dib


_





=
≥
−≤
'
'
'
7

−=−+⇔=++−⇔⇒≥ '''''''
n
g
hhnhh
__
=⇔+−=−+⇔ '''''
IP
<
bbdd_b_dbd_ ''''''' −−=−−−+−−⇔⇒−≤
n
g
_____
_
=⇔+−=−+⇔−=−−+−⇔ '''''''
I+/GP
*2.F T/+;'SN'S
n
g
MP70 U3#VW.X+4.,/@
o7  =
JY& V,
 ≥
690
 ≤

77  −−=
<=>D&J2M
eee
e__ −=−+− '''
7

=−−−⇔−=−+−−−+− '''''''''
61:  0
U,!5+:0 U Z*[ -V T\
 42.6]/  ? 8:0 U 
5 236^YG':;
7bde_
e
_
ee
e
_
ee
=⇔=−⇔−=++−−+⇔−=++− '''''''
)'SN/ 4'SN,!_.T6
P*"GU>;
eee
 =±
+0`C@ Y
 
bdebd
eee
 ±±±=±
#              "  2;



=±±
=±
777e
e

''
''




=
−
=
⇔
_
_
_g
'
'
7O&6"#D,<M
_='
'
_
_g−
='
7
)b
b_edbhdb_ehdm −−+=−−+⇔ ''''
b_ehb7d_ehdb_ehdm −++−−+=−−+⇔ ''''''



=⇔
=−++

<*"IMPR>5,>;
IMP
( ) ( )
( ) ( )
m
_
__e
b_de
eh
b_dh
m
_
__eeh
−
=
+−
−
−
++
−
⇔
−
=−−−−+⇔
'
'
'
'
''
''


++
'
'
'
db )b
_e_bed
__
≥−−− ''''
d_b
(.f2M
,bKM
−≥'
7
iO(Sk,*6)*/":7
iO(S≠
 ≠+−⇒ '
7A$8$Q'%4,),"$M
nehbdh
b7dbd
bd
_
__
__
<⇔<+⇔−>+−⇔−>
+−++
+−
'''''
''
''
7






≥≤
>−<
⇔
≥−
>−−
⇔ *''
*''
*''
''
''
7
O&6<4,)"#M
bpest_uv
_

pd +∞∪∪−−∞=)
7
Qua v d trên, lưu  cho hc sinh cc đim sau:
<=/>IMPW,!Vc 0W8Q# -++4..V
WA/5!&6
<75#0.-/A0F
/.?5'> d 8F? 690
'> d 8F?..-?+.
W86
<=>&"M

+−−−
=>
+−+−
=

'

'
7
"#D,<
dib⇔
D,<)<
−≥
7_
nhbhd
h
nhh
__
_
_



≤⇔
+−≥−
≤
⇔+−≥−⇔−≥⇔ .

.
'

_
+= '

≥

7K"D"#QM
7mllh_
__
±=⇔=+⇔=⇔=−+ ''
)b
eee
__
=−+−+⇔ ''''
;M
'' e
_
+=


≥

7"#QM
7
_
ge
_mememe
___
±−
=⇔=−+⇔=+⇔=⇔=−− '''''
<=>?&


≤−≤
≤+≤
mlm
mlm
lm
lm
.
.
.
.
7
-I23?&
7bvdbdsbdb7d_vbdbds =+++±± ''(''(''(.
*"G A;
7bdbd ''( ±=
$0g?h 8
i G+8R+G?IP 4
IP "6
<=>@&?M
7blbdedle ''.'' −++=−++
,bJ2H
e=.
7
)b
.
""#D<7
(.f2M;M
_gle
_



=
−=
⇔=−+
l
e
blbded
'
'
''
7
)b"#D<
bd⇔
D<
v_epes∈
7
xaM
g_bd
_
−−= (
'(
v_epes∈
,*6
bd(
"y)%
v_epes_lgb_edbdbedl ∈∀−=≤≤=−⇒ (((
7
c'&6
bd

K"DQM
m__
__
=⇔=−−⇔−= 
,6
m
=

'dib,"$M
em__e_
_
++=− '''




++=+−
≤≤−
⇔
__ng_lhh
j
__
''''
'



=+−
≤≤−
⇔

bd
bd
=
,"$

bd

=e
",+)&
,
7
,P;.M
7bdbd7bd7bd7 =++ ''(''(
<=>B&J2M
b_d_m
_e
+=+ ''
7
J2M

−≥
'
7,DM
bd_bd_bbddm
__
+++−=+−+⇔ ''''''
_


m


,DM




=
=
⇔=+−
_

_
_m_
_



7
i
Memhh


_
_
_
=+−⇔=
+−
+
⇔= ''
''

(.f2M;M
____
ehe__ ''''' −=++⇒−=+=
QM
e
____
=−−⇔−=+ 
_
_
m
_
_
m
_
−
+
=+⇔
+
=⇔ '''
7
J26,"$<
_
m+
='
'"6<./6*4,
"#7
<=>D&
.
",/D<M
h

'
.
'
'
7
;M


_



hh
>∀<<⇒
+
−=
+
−
= 
''
'

'QM
.

.
 −=−⇔=+ _e_e
_

dib

BC\ A6)3#/W8V,!??
h 80>?'.A/#
BC 86J"+/G':G -;
-I23A& 
7bdbdb7dbd7 =++ ''(''(
 O(.6,D";
bd'( =
H"D,"$ -M 
bdbd
_
=++ ''
7,2
6 S S,d+'[,D'[,
DSb8,!.6. ABC,!2 ?7
<=>E&J2M
__bd_
__
−−=−+− '''''
(.f2M;M
_
_
−+= ''
,"$M
hbd_
_
=−−− ''
76
)&,-D
_
bd{ +=∆ '

/> G/>+8>50/>+8>6
<=>F&J2M
__
_ '' =−+
7
*"/>#?5@>/A AB
C6^>0>,>H..C
E++..6)3#V?8c/;J7'>
dF
 ≤≤− '
50 U
__
 ' =−
# Y8c
/Vl 0!+8>5i/6*>
5;
KM
7≤'
;
vps
π
∈= '
7K"DQM
_

__
___
=⇔=−+⇔=−+ 
d.
b7 ≥

π
∈= '
<=>&J2M
bd_bd
_e_e
'''' −=−+
(.f2MKM
7≤'
;M
vps
π
∈= '
7QM
 7_bbdd_
ee
=−+⇔=+
_e_
_

7_b
_

d
_e
__
=−−+⇔
−
=
−
−⇔ 

_
b_d
_
__
''
'
''





−−−
=⇔
=−+−−
−≤
⇔
_
___
_b_d
_
_
'
''
'
9/>EC3#>/33 >">5
,> ?? 0#/> 8,2.,
5/>6)':EC;
<=>&J2M
'''' −+=−+ 


−+⇔
(
)



==
⇔




=−
=−
⇔=−−−⇔=−−−⇔
*9
*''
''
''
''''''''

_
e

e_ebd_
_
_
____
K%$'("=/H<,D<4,MSk'Sk7

−
+
_

_e
e


_
_




O&6,DM



=
=
⇔








=−

5/.V T0n^XYh5+W 8 
+ Y+8>;

__
=+
αα
6Jp 0>5;
;M






∈=
_
p
_
π
'
7d=/6$E'
[ ]
p∈'
b7
K"D"#QM
be_dbbddbdde7
e
_
 =−+−+−⇔+=+ 


kEC3#> ?5
!&6> .c[# +.>+/G_
 T/. T0>56
OPQR&
')*'C32H%+"HD"
'(!(D8')&D/P;
"=!>?,"@7O'&6"65"$=/56\/,
7\/.6!('&!(_56
PC~!)"#/3.'8/2
+[.,/•)P:,3'&Sa'
8/,5P;" D8H<')%'&."
2)&97€8"'(!(_%"
< .')*'CP
;7A, \/ '()'=')*
'C"=!'?,"@p"yP)R/3
.)&,'(=/2H,/7O('&6",
!('!(_"#D"$HU022)&'=5
6)%&.1)%",3,6)*
'C'=.\/ /3"#)%27
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')*'C33./\/,!
(D8')&D/7O'&6)2*
:!H.656!7
8"63H<4,)2H.6')*
'C!7W;.5/)2*GF!L
G@)'%F=/%56DZ'
)/7


.ST