MC vdi (O) (C la tiep diem) Ke CH vuong goc vdi AB (He AB), MB cat
2) a) Khim= 4, phiTdng tnnh (1) trdthanh x' 4x+ 3=
T a c 6 : a + b + c = l + (-4) + 3 = 0
Vay nghiem cua phiTdng tnnh la x, = 1 ; X2 = - = 3 . a b) A = - 4(m - 1) = m ' - 4m + 4 = (m - 2 ) ' > 0, phiTcfng trlnh c6 nghiem x,, X2 vdi moi m ;t 2. Theo he thtfc Wi-6t ta c6 : T ' ^ " [ X| X 2 = m - 1 Phtfdng tnnh c6 nghiem khac O o m - l ^ O o m ^ t l Do do : — + - L = ^' +^2 o ^' = ^1 +^2 ^ _ n L X, X2 2011 ^ x,X2 2011 ^ m. 2 0 1 1= m ( m - l ) o m( 2 0 1 1- m + l ) = 0 ^ r m = 0 ^ [ ' ' " = 0 (nhan) / . .2012 - m = 0 [ m - 2012 (nhan) • ; , ;, NhSnxet:
CJ tren da giai he phi/dng Irinh bac nhál hai an n^y bIng phiTdng phap cpng ^ai sọ Ban dpc hay giai b^ng phi/dng phap thẹ
m m- 1 2011
Luyjn giSi truOc k1 thi vao I6p 10 ba miln BJc. Trung, Nam mOn ToAn _ Nguyin Dure Ta'n
2) Day la bai loan van dung h? thiJc Vi-6t, can lUu y — + — c6 nghla o X| 0 va X2 ^ 0.
Bai 3: a) Bang gia tri :
X -4 -2 0 2 4
4 1 0 1 4
Do thi ham so :
b) (d) c^t true tung tai diem c6 tung do bkng -2 nen b = -2.
Diem thuoc (P) c6 hoanh do bing 2 thUung do cua diem do la - .2^ = 1. 4
3 3 Diem (2 ; 1) thuoc (d) o 1 = ạ2 - 2 o a = - . Vay a = - ; b = -2.
Nhan xet: Day la bai toan de ve do thi ham so y = ax^ (a ^ 0). Bai 4: a) ACB = 90" (goc npi tiep ch^n niJa difdng tr6n)
Tỉ gidc MCNH c6 : ' p
MCN + MHN = 90" + 90" = 180" nen npi tiep mot dU'dng tron. nen npi tiep mot dU'dng tron.
Mat khac AEB = 90" (goc npi tiep chin nufa dU'dng tron).
Taco : O D l A E ( g t) v a E B l A E( A E B = 90°). ^
VayOD//EB. , O b) Xet ACKD va ACEB CO :
iCCD = ECB (doi dinh), CD = CB (gt), CDK = CBE (so le U-ong va OD // BE) Do do : ACKD = ACEB (g.c.g) =^ CK = CE
Vay C la trung diem cua doan thSng KẸ
, _ . I 1 . c ^
CtyTNHH MTV DWH Khang Vijt
AEC = ABC (hai goc noi tiep cilng ch^n cung AC)
AEHK vuong tai H c6 HEK = 45" => AEHK vuong can tai H. . . . Ma HC la diTcJng trung tuyen cua tarn giac EHK. Do do HC la diTdng phan giac cua tam giac EHK KHC= iEHK = 45". i = ?!
Ma MNC = MHC (tur giac MCNH npi tiep) nen MNC = 45". Ta CO : MNC = ABC = 45", MNC va ABC dong vj. Vay MN // AB.
d) Xet AABD co AC, DO la hai diTdng trung tuycn (O, C Ian liTpl la trung diem cua AB, BD) c^t nhau tai M.
=> M la trong tarn cua tarn giac ABD => DM = — DO => — 3 DO 3 MN DM
Xet A DOB CO MN // OB => = — (he qua cua dinh li Ta-let) OB DO ^ ^ • \ MN 2 ^^^^ 2R
Nen = — => MN = —
R 3 3
Tu- giac MCNH npi tiep c6 M?iN = 90" =^ MN la difdng kinh cua diTdng tron ngoai tiep tiir giac MCNH => Ban kinh cua diTcJng tron ngoai tiep tỉ giac MCNH bang ^ : 2 = - .
^ 3 3 --^^ • t
. 7 1 = ^ ^ (dvdt)
Vay dien tich hinh U-on ngoai tiep tu" giac MCNH b^ng
V 3
Nhan xet: ,} ;r.
• Cic cau 1); 2); 3) de, quen thupc.
• Cau 4 la cau kho nhat cua bai toan 4, ph^t hien M Ik trpng tam cua tam giac
2R
ABD de CO MN // OB, tif do c6 MN = — giup c6 difpc M giai bai toan.
DE THI TUYEN SINH VAO LdP 10 THPT, TJNH DAKLAK NAM HQC 2011 - 2012
B&i 1: (2 diem) • '
1) Giai cac phúPng trinh sau ; ^ ^ ^ , a)9x' + 3 x - 2 = 0 b) x'+ 7x^- 18 = 0 " ^ ^ ' ! 2) Vdi gia tri nao cija m thi do thi hai ham so :
Bai 2: (2 diem)
1) Riit gon bieu thuTc : A = 1