kiểm tra 1 tiết đại 8 bài số 1

Tióỳt 21: Ngaỡy soaỷn:.1/11/ 2007

A. MUC TIU BAèI DAY :
- Nhũm kióứm tra laỷi kióỳn thổùc cuớa hoỹc sinh sau mọỹt
chổồng õaợ hoỹc, xem hoỹc sinh õaỷt kóỳt quaớ thóỳ naỡo sau thồỡi
gian hoỹc tỏỷp.
B. CHUỉN Bậ CUA GV VAè HS :
GV: óử kióứm tra in sụn.
HS: - Giỏỳy kióứm tra.
C. TIN HAèNH KIỉM TRA :
ệ
I, PHN TRC NGHIM: (3 im)
Cõu 1: Tớch ca n thc -5x
3
v a thc 2x
2
+ 3x - 5 l:
A) 10x
5
- 15x
4
+ 25x
3
. B) -10x
5
- 15x
4
+ 25x
3
. C) -10x
5

- 15x
4
- 25x
3
. D) Mt kt qu khỏc
Cõu 2: a thc 8x
3
- 12x
2
y + 6xy
2
- y
3
c thu gn l:
A) (2x + y)
3
. B) (2x - y)
3
. C) - (2x + y)
3
. D) (-2x + y)
3
.
Cõu 3: ng thc no sau õy sai ?
A) (a - b)
2
= (b - a)
2
. B) (a - b)
3

= (b - a)
3
. C) (a - b)
2
= (- a + b)
2
. D) (a - b)
3
= - (b - a)
3
.
Cõu 4: Tỡm x trong biu thc 2x (x - 3) + 5(x - 3) = 0 ta c:
A) x = 3 B) x = - 2,5 C) x = 3 hoc x = - 2,5 D) x = - 3 hoc x = 2,5
Cõu 5: Kt qu no sau õy sai ?
A) (-2x)
6
:(2x)
3
= -8x
3
. B) (xy)
10
:(xy)
7
= (xy)
3
C) y
7
: (-y)
4

= y
3
. D) 15x
7
: 3x
2
= 5x
5
.
Cõu 6: Biu thc khai trin v rỳt gn ca P = (2x + y) (4x
2
- 2xy + y
2
) l:
A) 2x
3
- y
3
. B) x
3
- 8y
3
. C) 8x
3
- y
3
. D) 8x
3
+ y
3

.
II, PHN T LUN (7 im):
Cõu 1: (2 im): Thc hin cỏc phộp tớnh nhõn sau:
a) 3x
2
(5x
2
- 4x + 3); b) (3x - y)(2x
2
- 3y
3
+ 5xy);
Cõu 2: (2 im): Tỡm x bit:
a) 3x(x - 2) - 2(2 - x) = 0 b) x
2
- 25 - (x + 5) = 0;
Cõu 3: (2 im): Phõn tớch a thc sau thnh nhõn t:
a) x
4
- 3x
3
- x + 3; b) x
2
+ 4x + 3;
Cõu 4: (1 im): Sp xp a thc theo lu tha gim dn ri lm phộp chia:
(12x + 5x
3
+ 14x
2
+ 8) : ( x + 2);

---------------- Ht --------------
AẽP AẽN VAè BIỉU IỉM
Gv Lờ Th Kim Oanh
KIỉM TRA CHặNG I (1
tióỳt)
I/ PHệN TRếC NGHIM :
Cỏu 1 2 3 4 5 6
aùp aùn B B B C A D
II/ PHệN Tặ LUN
Cỏu 1: (2 õióứm): Thổỷc hióỷn caùc pheùp tờnh sau:
a) 3x
2
(5x
2
- 4x + 3) = 15x
4
- 12 x
3
+ 9x
2
; (1 õióứm)
b) (3x - y) (2x
2
- 3y
3
+ 5xy) = 3x (2x
2
- 3y
3
+ 5xy) - y (2x

2
- 3y
3

+ 5xy)
= 6x
3
- 9xy
3
+ 15x
2
y - 2x
2
y + 3y
4
- 5xy
2
= 6x
3
- 9xy
3
+ 13x
2
y +
3y
4
- 5xy
2

(1

õióứm):
Cỏu 2: (2 õióứm): Tỗm x bióỳt
a) 3x (x - 2) - 2 (2 - x) = 0 (3x + 2) (x - 2) = 0 x = -2/3
hoỷc x = 2
(1 õióứm)
b) x
2
- 25 - (x + 5) = 0 (x - 5) (x + 5) - (x + 5) = 0 (x +
5) (x - 6) = 0
x = -5 hoỷc x = 6.
(1
õióứm):
Cỏu 2: (2 õióứm): Phỏn tờch õa thổùc thaỡnh nhỏn tổớ
a) x
4
- 3x
3
- x + 3 = (x
4
- 3x
3
) - (x + 3) = x
3
(x + 3) - (x + 3) = (x
+ 3) (x
3
- 1)
= (x + 3) (x - 1) (x
2
+ x + 1)

(1 õióứm)
b) x
2
+ 4x + 3 = x
2
+ x + 3x + 3 = (x
2
+ x) + (3x + 3) = x (x +
1) + 3 (x + 1)
= (x + 1) ( x + 3).
(1
õióứm):
Cỏu 2: (1 õióứm): Sừp xóỳp õa thổùc theo luyợ thổỡa giaớm
dỏửn cuớa bióỳn rọửi thổỷc hióỷn pheùp chia: (12x + 5x
3
+ 14x
2
+
8) : ( x + 2);
Sừp xóỳp: 12x + 5x
3
+ 14x
2
+ 8 = 5x
3
+ 14x
2
+ 12x + 8 0,25
õióứm
Thổỷc hióỷn pheùp chia:

-
5x
3
+ 14x
2
+ 12x
+ 8
x + 2
5x
3
+ 10x
2
5x
2
+ 4x + 4
-
4x
2
+ 12x
4x
2
+ 8x
-
4x +
8
4x +
8
0
Vỏỷy (12x + 5x
3

+ 14x
2
+ 8) : ( x + 2) = 5x
2
+ 4x + 4
0,75
õióứm

HặẽNG DN Vệ NHAè :
- Laỡm caùc laỷi baỡi tỏỷp kióứm tra.
- Xem baỡi mồùi Phỏn thổùc õaỷi sọỳ
Gv Lờ Th Kim Oanh