D B1 OB^ CH ± OBC HO =90 "
HirdNG DAN GIA
<1 2 4Vr '2aVa 4Vr '2aVa
- 1 N/a + 1
+ if - (>/a - l)^ + 4VI(a - 1) 1
luy^n giai dg trade ki thi vao Iflp 10 ba mign BJc. Trung, Nam mfin Toin _ Nguyfin Pile l a p — _ a + 2V^ + l - a + 2 N / I - l + 4a>/^ - 4^1 _ J _ 4 a V ^ 2) Dieu kien a > 0, a 1. •2aVa (a-l).2â/a a - 1 P = a o a - 1 o 2 = a ^ - a < : ^ a ^ - a - 2 = 0
< = > a - 2 a + a - 2 = 0<=>(a- 2)(a + 1) = 0 <;> a = 2 hoSc a = - 1 a = 2 (thoa dieu kicn a > 0, a ;t 1); a = - 1 (khong thoa dieu kien a > 0) Vaya = 2 t h i P = a "
Nhan xet: Day la bai loan de, quen thuoc doi vdi mpi hoc sinh Idp 9.
C§u 2. J
1) PhiTdng trinh hoanh dp giao diem cua (d) (P): = 2x + 3 X ' - 2x - 3 = 0 = 2x + 3 X ' - 2x - 3 = 0
j. a - b + c = l - (-2) + (-3) = 0
Xi = - 1 , X i = — = 3
Vay (d) va (P) c6 hai diem chung phan bicl 2. X, = - 1 ihi y, = xf = 1 => A ( - l ; l )
X2 = 3 thi y 2 = x^ = 9 =^ B(3;9) ° Vay (d), (P) CO hai diem chung phan
bictla A ( - l ; 1);B(3;9) Vc A H l O x l a i H , B H l O x lai K. Ta c6 A H = 1 , 0 H = 1,0K = 3, BK = 9; AH 1 Ox, BK l O x => AH//BK _ (AH + BK)HK ^ (1 + 9).4 ^ ^AHKB *• — 1 27 SKOB = - O K . B K = — ^
SoAB = SAHKB - (SHAO + SKOB) = 6 (dvdt)
Nhan xet: V i A ( - l ; 1), B(3; 9) ncn gpi H, K Ian liTPt \h hinh chieu cua A, B
trcn true hoanh, ta c6 H ( - l ; 0), K (3; 0). Tif do giup tinh di/dc dien lich tam giacOAB.
Cau 3.
1) Vdi m = 4, ta c6 phi/dng Irinh: x^ + 8x + 12 = 0
A '= 1 6 - 1 2 = 4, V A^ - 2 Phi/dng irinh c6 hai nghiem phan bi(?t Phi/dng irinh c6 hai nghiem phan bi(?t
* • ....
Cty TNHH MTV DWH Khang Vi^t
- 4 + 2 ,
x, = — : — = - 2 . = : = - 6 ^ - 2
1 " 1