C. CAU HOI VA BAITAP
c) Tim diimM tre nA sao cho AM ngin nhit.
3.3. Lap phuong trinh tdng quat cua dudng thing A trong mdi trudng hgp sau :
a) A di qua diim M(l ; 1) va cd vecto phap tuyln n = (3 ; - 2) ; b) A di qua diim Ă2 ; - 1) va cd he sd gdc k = ;
c) A di qua hai diim Ă2 ; 0) va B(0 ; - 3).
3.4. Lap phuong trinh ba dudng trung true ciia mdt tam giac cd trung diim cac
canh lin lugt la M ( - 1 ; 0), N(A ; 1), P(2 ; 4).
3.5. Cho diim M(l ; 2). Hay lap phuong trinh cua dudng thing qua M va chin tren hai true toa đ hai doan cd đ dai bing nhaụ tren hai true toa đ hai doan cd đ dai bing nhaụ
3.6. Cho tam giac ABC, bilt phuong trinh dudng thing A B : x - 3 y + l l = 0 , dudng cao AH : 3x + 7y - 15 = 0, dudng cao BH : 3x - 5y + 13 = 0. Tun dudng cao AH : 3x + 7y - 15 = 0, dudng cao BH : 3x - 5y + 13 = 0. Tun
phuong trinh hai dudng thing chiia hai canh cdn lai ciia tam giac.
3.7. Cho tam giac ABC cd A ( - 2 ; 3) va hai dudng trung tuyln : 2 x - y + l = 0 v a
X + y - 4 = 0. Hay vilt phuong trinh ba dudng thing chiia ba canh cua tam giic.
3.8. Vdi gia tri nao eua tham sd m thi hai dudng thing sau day vudng gdc :
Ạ :mjc + y + ^ = 0 va A2 : x - y + m = 0 ?
3.9. Xet vi tri tuong đ'i ciia cac cap dudng thing sau day : rx = - l - 5 r fx = - 6 + 5f rx = - l - 5 r fx = - 6 + 5f a) d: \ vk d': \ [y = 2 + 4r [y = 2-At; (x = l-At h) d: < vk d' •.2x +Ay-10 = 0; ^ \y = 2 + 2t
3.10. Tim gdc giiia hai dudng thing :
rf, : X + 2y + 4 = 0 va rfj = 2x - y + 6 = 0.
3.11. Tfnh ban kfnh cua dudng trdn cd tam la diim /(I ; 5) va tiSp xiic vdi dudng thing A : 4x - 3y + 1 = 0.
3.12. Lap phuong trinh cac dudng phan giac ciia cic gdc giiia hai dudng thing AJ : 2x + 4y + 7 = 0 va A2 : x - 2y - 3 = 0.
3.13. Tim phuong trinh ciia tap hgp cac diim each diu hai dudng thing : AJ : 5X + 3y - 3 = 0 va A2 : 5x + 3y + 7 = 0.
3.14. Vilt phuong trinh dudng thing di qua diim M(2 ; 5) va each diu hai diim A ( - l ; 2 ) v a B ( 5 ; 4 ) .