DKT 45 dai so 8 BS2 HK 2

<span class='text_page_counter'>(1)</span>PHÒNG GD& ĐT LANG CHÁNH TRƯỜNG THCS TRÍ NANG. ĐỀ KIỂM TRA Năm học: 2011 - 2012 Môn : Đại số (Thời gian làm bài 45 phút). Họ và tên HS:.................................................................................................... Lớp: 8. Điểm:. Lời phê của giáo viên.. Đề bài: Câu 1: (2đ). Cho m > n, hãy so sánh 8m - 2 với 8n - 2. Câu 2: (3đ). Giải bất phương trình và biểu diễn tập nghiệm trên trục số. a) 2x - 7  0. b) - 3x + 9 > 0. Câu 3: (3đ). Tìm x sao cho. a) Giá trị của biểu thức 2 - 5x nhỏ hơn giá trị của biểu thức 3(2 - x). 5x  2 b) Giá trị của biểu thức 3 không nhỏ hơn giá trị của biểu thức x + 1.. Câu 4: (2đ). Giải phương trình  x + 5 = 3x - 2. 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<span class='text_page_counter'>(3)</span> * MA TRẬN VÀ ĐÁP ÁN: 1) Ma trận: Nội dung Bất đẳng thức. Nhận biết. Thông hiểu C1 2. Bất phương trình bậc nhất một ẩn. Vận dụng. Tổng 1 2. C2. 1 3. C3. 3 1. 3 Phương trình chứa dấu giá trị tuyệt đối Tổng:. C4. 3 1. 2 1. 3 2. 2 4. 8. 10. 2) Đáp án: Câu 1: (2đ). a) Nhận định 8m - 2 > 8n - 2. b) Suy luận chứng tỏ nhận định. (Từ m > n, nhân hai vế với 8, sau đó cộng cả hai vế với - 2). Câu 2: (3đ). a) 2x - 7 ≤ 0  2x ≤ 7  x ≤ . Phương trình có tập nghiệm là: S = {x/ x  } b) - 3x + 9 > 0  - 3x = - 9  x < 3.Phương trình có tập nghiệm là: S = {x/ x < 3} Câu 3: (3đ). a) 2 - 5x < 3 (2 - x)  2 - 5x < 6 - 3x  - 5x + 3x < 6 - 2  - 2x < 4 x>-2 b)  x + 1  5x - 2  3x + 3  5x - 3x  3 + 2  2x  5  x Câu 4: (2đ). Giải phương trình  x + 5 = 3x - 2. Ta có: +)  x + 5 = x + 5 Khi x + 5  0 hay x  - 5 +)  x + 5 = - ( x + 5 ) Khi - x - 5 < 0 hay x <- 5 * Phương trình: x +5 = 3x -2 với x  -5. Ta có : x +5 = 3x -2  x -3x = - 2 - 5  - 2x = - 7  x= Giá trị x = TMĐK, vậy là nghiệm của pt. * Phương trình: - x - 5 = 3x -2 với x < -5. Ta có: - x - 5 = 3x -2  - x - 3x = - 2 + 5  - 4x = 3 x= Giá trị x = không TNĐK, ta loại. Vậy tập nghiệm của pt là: S = { }..

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