Đề khảo sát chất lượng toán 8

TRNG THCS.............................
PHIU KHO ST CHT LNG
H v tờn: .........................................
Mụn : Toỏn 8
Lp: 8 ........
Nm hc: 2012 - 2013.
A
Thi gian: 30 phỳt (khụng k giao )
im
Ch ký giỏm kho
Ch kớ CB coi thi

I. PHN TRC NGHIM: (3 im)
Hóy khoanh trũn ỏp ỏn m em cho l ỳng trong cỏc cõu sau:
Cõu 1. Nếu (2x+3)2 = 4x2+ ax + 9 thì a bằng:
A.2
B.3
C.12
D.6
3
3
2
Cõu 2. Nếu (2x-3) = 8x - 36x + ax-27 thì a bằng:
A.6
B.18
C.36
D.54
Cõu 3. Kết quả khi phân tích đa thức 3xy2 + 6xyz thành nhân tử là:
A. 3xy ( 3y + z)

B . 3xy ( y + 3z)

C . 3xy ( y + 2z)

D. 3xy ( 2y + z)

Cõu 4. Kết quả khi phân tích đa thức 4x2-1 thành nhân tử là:
A. (2x+1)(2x-1)
B. (4x-1)(2x+1)
C. (2x-1)(2x-2)
D.
(4x-1)(2x+2)
Cõu 5. Hình thang ABCD có AB // CD ; AB = 8 cm ; CD = 10 cm , đờng
trung bình của hình thang ABCD bằng :
A. - 9 cm
B. 9 cm
C. -18 cm
D. 18 cm
Cõu 6. Cho tam giác ABC có M, N lần lợt là trung điểm của AB, AC và BC
= 6cm . Khi đó độ dài đờng trung bình MN bằng:
A. 12 cm.
B. 6 cm
C. 3cm
D.Không xác định đợc
II. PHN T LUN: (7 im)
Cõu 1. (2 im). Phân tích các đa thức sau thành nhân tử:
a. 5x + 10 + x( x + 2)
b. x2 + 4x - y2 + 4
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Cõu 2. (2.5 im). Tìm x biết:
a) x2 + 2x + 1 = 0
b) x2 + 5x = 6
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Cõu 3. (2.5 im). Cho tứ giác ABCD, gọi E,F,G,H lần lợt là trung điểm của
AB , BC, CD, và DA. Chứng minh rằng EFGH là hình bình hành.
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TRNG THCS.............................
PHIU KHO ST CHT LNG
H v tờn: .........................................
Mụn : Toỏn 8

Lp: 8 ........
Nm hc: 2012 - 2013.
B
Thi gian: 30 phỳt (khụng k giao )
im
Ch ký giỏm kho
Ch kớ CB coi thi

I. PHN TRC NGHIM: (3 im)
Hóy khoanh trũn ỏp ỏn m em cho l ỳng trong cỏc cõu sau:
Cõu 1. Nếu (2x-3)2 = 4x2- ax+9 thì a bằng:
A.-2
B. 3
C. 6
D.
12
Cõu 2. Nếu (2x+3)3 = 8x3+ 36x2+ ax+27 thì a bằng:
A.-6
B. 18
C . 54
D.-36
Cõu 3. Kết quả khi phân tích đa thức 3xy2 - 6xyz thành nhân tử là:
A. 3xy ( 3y - z) B . 3xy ( y - 3z) C . 3xy ( y - 2z)
D. 3xy ( 2y - z)
Cõu 4. Kết quả khi phân tích đa thức 9x2-1 thành nhân tử là:
A. (3x-1)(3x-2)
B. (9x-1)(3x+1)
C. (9x-1)(9x+1)
D.
(3x-1)(3x+1)

Cõu 5. Hỡnh thang ABCD coự AB // CD ; AB = 5 cm ; CD = 7 cm , ủửụứng
trung bỡnh cuỷa hỡnh thang ABCD baống:
A. 5 cm
B. 7 cm
C. 6 cm
D. 12 cm
Cõu 6. Cho tam giỏc ABC cú BC = 6cm . Khi ú di ng trung bỡnh MN bng:
A. 12 cm.
B. 6 cm
C. 3cm
D.Khụng xỏc nh
c
II. PHN T LUN: (7 im)
Cõu 1. (2 im). Phõn tớch cỏc a thc sau thnh nhõn t:
a. 5y - 10 + y( y - 2)
b. y2 - 4y - x2 + 4
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Câu 2. (2.5 điểm). Tìm y biết
a) y2 - 2y + 1 = 0
b) y2 + 4y =5
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Câu 3. (2.5 điểm). Cho tứ giác MNPQ, gọi I,J,H,K lần lượt là trung điểm của MN, NP,
PQ, và QM. Chứng minh rằng IJHK là hình bình hành.
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P N- BIU IM
Toỏn 8
A
I. PHN TRC NGHIM: (3 im)
Mi cõu tr li ỳng c 0,5 im
Câu
1
2
3
4
5
6
Đáp án
C
D

C
A
B
C
II.Tự luận (7 im).
Cõu 1. (2 im). Phõn tớch cỏc a thc sau thnh nhõn t:
a. 5( x + 2) + x( x + 2)
(0,5đ)
=(x+2)(5+x)
(0,5đ)
2
2
b. x + 4x - y + 4
= (x+2)2 - y2
(0,5đ)
= (x + 2 + y). (x + 2 - y)
(0,5đ)
Cõu 2. (2.5 im). Tỡm x bit:
a) a) x2 + 2x +1 = 0
(x+1)2= 0 (0,5đ)
x = -1(0,5đ)
Vy x = -1
b) x2 + 5x = 6
x2 + 5x 6=0
x2 x + 6x 6=0
(0,5đ)
2
(x x )+ (6x 6)=0
x(x 1 )+ 6(x 1)=0
(x - 1)(x + 6) =0

(0,5đ)
x-1 =0 hoặc x+6 =0
* x-1 =0 x=1
* x+6 =0 x=-6
Vy: x =1; x = -6
(0,5đ)
Cõu 3. (2.5 im). Cho t giỏc ABCD , gi E,F,G,H ln lt l trung im ca AB ,
BC, CD, v DA. Chng minh rng EFGH l hỡnh bỡnh hnh.
Vẽ hình, viết GT,KL
(0,5đ)
ABC => EF // =

1
AC
2

Tơng tự => GH // =

1
AC
2

Vì : EF là đờng trung bình của

(0.75

đ)
đ)
=> EF //= GH
(0,5đ)

vậy tứ giác EFGH là hình bình hành.

(0.75


ĐỀ B
I. PHẦN TRẮC NGHIỆM: (3 điểm)
Mỗi câu trả lời đúng được 0,5 điểm
C©u
1
2
3
4
5
§¸p ¸n
D
C
C
D
C
II.Tù luËn (7 điểm).
Tương tự đề A
- Học sinh làm phương pháp khác nếu đúng vẫn cho điểm tối đa
- Điểm làm tròn đến 0.5

6
D