- Hai tieu diim : F^(S ;0), F2(S ;0).
vay Acd toa do la 1-V71 r, f, i+j^'
l + Jl ; , B cd toa do la 1-V7;
CAU HOI T R A C NGHlfiM
3.46. BA = (-2 ; 2)
'BC =.(2; 2)
'BẠ'BC =0=> ABC = 90°.
Dudng trdn ngoai tilp cd tam la trung diim / cua AC ntn cd toa đ (3 ; 4).
Chgn(D).
3.47. Chgn (A).
a, •
3.48. Dudng thing A : 6x - 4y - 12 = 0 cit Ox vk Oy lin lugt tai Ă2 ; 0) va
B(0;-3).
Ta CO AB = Jl3: Chgn (Q.
3.49. Chgn (A).
3.50. Dudng thing A:2x + y - 4 = 0 song song vdi d u ^ g thing d:Ax + 2y+ 1=0
vk di qua diim M ( l ; 2). Chgn (C).
3
3.51. Dudng thing A : 3x + 5y + 2006 = 0 cd he sd gdc lkk= — .Phat bilu (C)
saị Chgn (C).
3.52. Diim C(2; 2) cd toa đ thoa man phuong trinh dudng thing A: x - 2y + 2 = 0.
Ta lai ed TlC = (1 ; -2), n^ = (1 ; -2) suy ra MC vudng gdc vdi Ạ Vay
C(2 ; 2) la hinh chilu vudng gdc cua M xudng Ạ Chgn (C).
3.53. Dudng thing A di qua Ăl ; 1), B(2 ; 2) cd. vecto chi phuong AB = (1 ; 1).
^ {x = l + t
vay A ed phuong trinh tham sd -^
b=i+^
Diim 0(0 ; 0) thoa man phuong trinh cua A (dng vdi t = -1). Vay phuong , , , , \x = t
tnnh tham sd cua A cd the viet la < {y = t.
Chgn(D).
3.54. K = d(0;A)= , ^^ = 10.
V64 + 36 Chgn (D).
1-6 1
3.55. cos(A A-)= ^L— ^—= = -f=.
^ ^ JI + AJI + 9 J2
Chgn(C).
3.56. (Ox, AJ ) = 45°, (Ox, Â) = 60°. Suy ra (Aj, A2) = 15°. Chgn (B).
3.57. Phuong tiinh x^+y^+x + y + 2 = 0 khdng la phuong trinh cua dudng ti-dn
vi khdng thoa man dilu kien a + fe - c > 0. Chgn (B).
3.58. Toa đ ba diim Ă-2 ; 0), B(>^; V2), C(2 ; 0) diu thoa man phuong trinh
dudng ti-dn x^ +y^ = 4. Chgn (A).
3.59. Dudng ti-dn ndi tilp tam giac OAB cd tam I(a ; a). Ta ed d(I, AB) = d(I, Ox)
suy ra 7(1 ; 1). Ta cd B = d(I, Ox) = l.
vay phuong trinh cua dudng trdn ndi tilp tam giac OAB lạ:
• x ^ + y ^ - 2 x - 2 y + 1 = 0 . Chgn (C).
3.60. (Cj) cd tam /i(-l ; 3) va bdn kfnh Bj = 2.
(C2) cd tam /2(2 ; -1) vk ban kfnh B2 = 3.
Tacd/j/2=Bj+B2.
vay (Cl) tilp xiic ngoai vdi (Cj). Chgn(D).
3.61. Tilp tuyln A cd vecto phap tuyln OM^ = (1 ; 1).
Phuong trinh A cd dang l . ( x - l ) + l . ( y - l ) = 0 hay X + y - 2 = 0. Chgn (A).
3.62. IM>R suy ra diim M nim ngoai dudng trdn. Chgn (C).
3.63. Dudng ti-dn (C) di qua gd'c 0(0 ; 0). Cljgn (B). 3.64. Chgn(B). 3.64. Chgn(B).
3.65. Chgn (C).
3.66, (F) di qua cac diim Mj, Mj, M3. Chgn (D). 3.67, Chgn(D). 3.67, Chgn(D).
3.68, Chgn(C).
3.69, (C) tilp xuc vdi (F) tai Ai(-5 ; 0) va A2(5 ; 0). Chgn (C).
3.70, J(Fi, A) X d(F2, A) = b^ = 9. Chgn (B).
3.71, 0A = OB = OC = 3. Dudng trdn ngoai tilp tam giae ABC cd phuong trinh
x^ + y^-9 = 0. Chgn (D).
3.72, AtiépxucvdiC(0; l)<=>rf(C; A ) = l
<» \m\ = Ị
Chgn (A).
BAI TAP CUOI N A M
1, Trong mat phing Oxy cho tam giac ABC, bilt dinh Ăl ; 1) va toa đ trgng tam G(l ; 2). Canh AC vk dudng trung true cua nd lin lugt cd
phuong trinh lax + y - 2 = 0 v a - x + y - 2 = 0. Cac diim M va  lin lugt la
trung diem eiia BC va AC.
a) Hay tim toa do cac diim M va Ậ
b) Vilt phuong trinh hai dudng thing chiia hai canh AB vk BC.
2, Trong mat phing Oxy cho tam giac ABC cd AB = AC, BAC = 90°. Bilt (2 ^
M(l ; -1) la trung diem canh BC va G — ; 0 la trgng tam tam giac ABC. Tim toa do cac dinh A,B,C.
3. Cho ba diim Ă 1 ; 2), B(-3 ; 1), C(4 ; -2).
V •> 9 9 9
a) Chiing minh rang tap hgp cae diem M(x ; y) thoa man MA + MB = MC
la mdt dudng trdn.
b) Tim toa đ tam va ban kfnh cua dudng trdn ndi tren.
4. Cho hai diim Ă3 ; -1), B(-l ; -2) va dudng thing d ed phuong trinh
X + 2y + 1 = 0.
a) Tim toa đ diim C tren dudng thing d sao cho tam giac ABC la tam gide can tai C.
b) Tim toa đ eiia diim M ti-en dudng thing d sao cho tam giac AMB vudng
taiM.
Trong mat phing Oxy cho dudng trdn (J) cd phuong trinh
x2 + y2 - 4x - 2y + 3 = 0.
a) Tim toa do tam va tfnh ban kfnh ciia dudng trdn (F).
b) Tim m dl dudng thing y = x + mc6 diem chung vdi dudng trdn (T).
e) Vilt phuong trinh tilp tuyln A vdi dudng trdn (T) bilt ring A vudng gdc
vdi dudng thing dcd phuong tri n h x- y + 2006 = 0.
Trong mat phing Oxy cho elip (F) cd tieu diim thii nhat la (-V3 ; 0) va di
V^^
qua diem M 1;
a) Hay xac dinh toa do eac dinh cua (F). b) Viét phuong trinh chfnh tic ciia (F).
c) Dudng thing A di qua tieu diim thur hai cua elip (F) va vudng gdc vdi
true Ox va cit (F) tai hai diim C va D. Tfnh do dai doan thing CD.