Trường THCS định tăng bài kiểm tra 15 phút
Năm học: 2014 – 2015 Môn: Đại số 9. Tiết 56.

Họ và tên :............................................................ Lớp :...........






Đề bài:
Bài 1(6 điểm).
a) Điền biểu thức thích hợp vào dấu ( ... )
Giải phương trình bậc hai ax2 + bx + c =0 ( với a khác 0) theo (, ta thực hiện như sau:
-Bước 1: Xác định giá trị của các hệ số
-Bước 2: Tính giá trị của ( theo công thức ( = .......................
-Bước 3: So sánh giá trị của ( với số 0.
- Bước 4: Tìm nghiệm của phương trình như sau:
+ Nếu ( > 0 thì phương trình có 2 nghiệm phân biệt là
x1 = x2
+ Nếu ……… thì phương trình có nghiệm kép là
x1= x2=
+ Nếu ( < 0 thì phương trình ………………..

b) Giải phương trình 3x2 – 2x – 1 = 0.

Bài 2 (4 điểm). Cho phương trình sau : ( với m là một số bất kì)
a, Giải phương trình với m = 2b, Tìm giá trị của m để phương trình có nghiệm kép.
Bài làm:

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