..Theg d6nh gi6 cria T6 soan th6o dd thi, n6u s?p 46p c6c bhi tflp trong dd thi theo thri tu tri
dO den kh6 thi tht tg d6 sE ld: Cdu 2 - Cdu 3
-Cdu1-CAu5-Ciu4.
Trong de ti kh6ng c6 nhfing bdi to6n qu6
kh6 nhu CAu 5 cira cl6 thi nlm 2009, d6ng
thoi Cdu 2 cira dA thi n[m nay d6 hon CAu 2
(c6u dE nh6t) cira d6 thi n6m iru6c. Nhu th.5, x6t dudi g6c rlQ chuy6n m6n, d6 thi n6m nay nhe nhhng hon d6 thi nim 2009.
o Theo d6nh gi6 cua T6 ch6m thi, OC tfri Oam
bio tinh chfnh- x6c khoa hoc, dring c6u trdc quy
TORN HO(
dinh cua B9 GD&DT (ve ninfr thuc cfing nhu
vC bdn chdt to6n hgc), phir hqp c6c yOu ciu d6i
v6i m6t hgc sinh gi6i Qu6c gia m6n Todn cdp
THPT, c6 kh6 n[ng phdn lopi thi sinh.
..C6 y.ki6n ring nhi0u.thf sinh vi ngay vio
dAu bu6i thi da bi "sa 16y." o CAu I (do.ngh| day h cdu dd nhit cua ii),"cn bi uc ch6 tdm
li, gdy,inh huong khdng t6t toi viqc lhm-bii thi. N6u d6y li su.that thi di6u ndy chg thQl ci{c thi sinh d6 thi6u su chudn bi t6t (vC kiCn
thirc hoflc vA tAm lf thi, vA c6ch l]rm bai thi)
cho ki,thi,.d6ng thoi chua quan
-t6m dfng
mirc d6n CAu trric cua tl6 thi mh B0 GD&DT
dd th6ng bd'o t6i cdc thi sinh thdng qua cdc co quan quin lf gi6o dgc cria c6c dcrn vf dg thi,
vi c6c 16 sau:
+ C5u trfc.cira d€ thi kh6ng.y6u cAu cdc bbi tap trong de phai clugc s6p x6p theo thri t.u tu aE d6n kh6, md An dinh cdu thu bao nhiOu
phni lh bAi t4p thu6c phdn m6n nho;
+ MQt thf sinh dugc chuAn bi t6t vA tdm lf thi, vO c6ch ldm bii thi sE doc cAn thin tohn b0 dO
thi tru6c khi ldm bii, bi6t can OOi thoi giantrong qu6 trinh lhm bhi, ... ; trong qu6 trinh lhm bhi, ... ;
+ MQt hoc sinh gi6i To6n, dr.rgc chuAn !i OAV clu vC chuy6n m6n cho ki thi Fh6ng th_6 kh6ng
nhdn thdy Cdu2lh cAu dC nhdt trong d€,
. Ch6t lugng lim.bii cta thf sinh trong ki.thi
ndm nay lh m6t ddu hiQu cho th6y su di xu6ng cua phong trbo ho.c sinh gioi To6n trong mdy
nim gdn dAy. Nh[m mgc dich ngin ch[n xu
th6 nhy, gi6p phong trho h6i phl,rc vd ph6t tri6n, T6 chdm thi tld nhdt tri ki6n nghi c6c
cilp c6 thAm quyAn c6 griri ph6p hiru hiQu c6
vfr, khich lQ hgc sinh gioi say m6 hgc To6n vh
tfch cgc tham gia thi chgn hoc sinh gioi Qudc gia .m6n Torin (ching han: kh6i phuc cdc
quy.en lqi dd c6 d6i vdi cdc hgc sinh dopt giii
QuOc gia, ... ),
. Ngodi gini ph6p mb Td ch6m thi tta ki6n
nghf n6u trOn, c6 thd cbn nhirng gidi ph6p
kh6c dO cii thiQn thuc trang hiQn nay cita phong trbo hgc sinh gioi To6n. Tuy nhi€n, trong c6c giii ph6p d6 kh6ng !tl.g gi6i ph6p
bi6n dO thi chgn hgc sinh gioi Qu6c gia m6n To6n thhnh mQt dC thi c6 chdt luong chuy6n m6n tuong.duong m6t cl6 thi tuy6n sinh Dgi hgc, Cao d[ng (m6n To6n) hay mQt d6 thi t6t
nghiQp THPT (m6n To6n).
PARABOL... Qiep trang 3)
2. K,i AH vd
BK vudng g6c
voi truc hodnh
(H vd K thu1cOx). Tir d6 cdc Ox). Tir d6 cdc
bqn c6 the
khdm phd thAm
m1t di€u li thti ntra. "Tam gidt IHK vu.6ng tqi I chdng?"
Th4t vdy, hQ s6 g6c cira dudng thdng IH lit
Jt-tn - lr =1,[-!)=-,.xt-xn -xs a \ a) k xt-xn -xs a \ a) k
He sO g6c ctra cluong thing 1r( ln
lr-!rc - lt -1 .f I )-,.
"-*- -.r-; lA )-"
Tri d6 suy ra /Il vu6ng g6c v6i IK (h.4).
B4n dgc cfing c6 th6 chring minh ring LOIK
<n A,OHI, tir d6 suy ,u fiiR= 90o, hopc c6
th6 sir dpng dinh lf Pythagore dio.
DOn ddy c.rc ban c6 thd ki6m ra lai ktit qu6 cria
bii to6n bing c6ch cho a mQt gi6 ri nio d6.
3. Gpi C ld siao di6m cfia IH vd OA. Gpi D ld giao di6m cila IK vd OB thi ilr gidc ICOD ld
hinh gi?
4. Biy gid ta hfly thinh lap bni to6n nguqc. Cho Parabol y - a* trAn mQt phdng toa dA
/ r\
Oxy vd di€m I IO;] I , Vd dudng thdns (A
' \ a)
bdt tcr, qua I cdt hai nhdnh cila (P) tqi A vd B.
Hdy chtrng minh tam gidc OAB vubng tqi O.
C6c em hay Lu gi6i phin 3. vh 4. nh6.
Qua bhi todn trOn, chic Ban c19c dE th6y dugc "cdi dep" cira di6m t rOi ctru. Tqa d0l [Ot1j
tuy thuQc vho hq s6 a cua (P) \ a )
H6y rg d6t cho di6m dflc biQt nby mQt ten
ri6ng... md ban thfch.
Hinh 4
"r rrn,n*oro,
T9[H,HS
rl
Iup rhi T0All Hg( uu IUdl TRiMu*ematits ond Youth ltlugozine Mu*ematits ond Youth ltlugozine
xufr nAN rtJ Dot
So' 394 (4.2010) Ioa soan : 1878, pno- Gidng Uo, He Noi
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Hot odNc ntflt't rdp
tdng biAn nip : PGS S. PHAN OOAN THOAI rhrirdng bi€n tlip; IS. PHAM TT{I BACH NGoC Thrt kiTia soan : fAS. Ud eUANG VINH
rs. rnAN oiNu cuAu, ras. NcuvEN aNu otrNc, rs. rniN Neu o[rNc, rs. NcuyEN MrNH Dttr, rs. NcuyBN
MINH HA, rs. NcuvpN vmr uAt, pcs. rs: r-e qudc uAN, ras. pHeu vAN silNc, pcs. rs. vu rHaNH *i91,
Gs. rsKfl. NcuvEN vAN uAu, Ong NGu_vEN rHAc umu, rs. rnAN uOU uau, pcs. rs. NcuvgN oANCilft:
PGs. rs. TA DUY PHUONG, rls. NcuvEN ru6 rnecu, GS. TSKH. DANG HUNG rsANc, rus. v0 rrv rnUy,
pcs. rs. vfr DUONG THUy, GS.TSKH. Nco vrpr TRUNG.
BAN CO VAN KHOA HOC
GS. T sKH.NcuyEN cArw roaN
GS, T SKH. TRAN VAN NHTINGTS.NCUYENVANVONG TS.NCUYENVANVONG
cs.ooaNquiNn
- PGS S.TRANVANHAO '
cHru rnAcru Nrufitt xuir nAx