Thể loại Giáo án bài giảng Đại số 8
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Ngày tạo 11/7/2012 3:52:46 PM +00:00
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TRƯỜNG THCS VÕ THỊ SÁU ĐỀ KIỂM TRA CHƯƠNG I
TỔ: TOÁN – TIN –LÝ – CN MÔN: ĐẠI SỐ 8
( Thời gian: 45 phút không kể thời gian giao đề)
Họ và tên:…………………………. Lớp:……….. |
Điểm |
Lời phê của giáo viên
|
Bài 1:( 2 điểm) Thực hiện phép tính
a) 7x(2x-5)+(4x – 3)(x + 2) – 16x2
b) (x + y)( x2 – xy + y2) +(x – y)( x2 +xy +y2)
Bài 2: (3,0 điểm) Phân tích các đa thức sau thành nhân tử:
a) 5x2y + 10xy2 ;
b) x3 + 2x2 + x
c) xy + y2 – x – y
Bài 3: (2 điểm) Tìm x, biết:
a) 3x3- 12x = 0
b) x2 – 5x – 6 = 0
Bài 4: (1,5 điểm ) Tính giá trị của đa thức:
x2 – 2xy – 9z2 + y2 tại x = 6 ; y = - 4 ; z = 30.
Bài 5: (1,5 điểm ) a) Tìm a để đa thức x3 + x2 – x + a chia hết cho x + 2.
b) cho a2 + b2 + c2 = ab + bc + ca. Chứng ming rằng a = b = c
BÀI LÀM
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Đáp án và biểu điểm
Bài |
Ý |
Nội Dung |
Điểm |
1 |
1a 1b |
x2 – 30x - 6 2x3 |
1,0đ 1,0đ |
2 |
|
|
3đ |
|
2.a |
5x2y + 10xy2 = 5xy(x + y) |
1,0 đ |
2.b |
x3 + 2x2 + x = x(x2 + 2x + 1) = x(x + 1)2 |
0.5đ 0.5đ |
|
2.c |
xy + y2 – x – y = y(x + y) – (x + y) = (x + y)(y – 1) |
0.5đ
0.5đ |
|
3 |
|
|
2đ |
|
3.a |
3x3 – 12x = 3x(x2 – 4) = 0 3x(x – 2)(x + 2) = 0
|
0.25đ
0.5đ 0.25đ |
3.b |
x2 –5 x – 6 = 0 x2 – 6x + x - 6 x(x – 6) + (x - 6) = 0 (x – 6)(x + 1) = 0 x = 6 x = - 1 |
0.25đ 0.25đ 0.25đ 0.25đ |
|
4 |
|
|
2đ |
|
|
x2 – 2xy – 9z2 + y2 = (x2 – 2xy + y2) – 9z2 = (x – y)2 – (3z)2 = (x – y – 3z)(x – y + 3z) Thay x = 6 ; y = - 4 ; z = 30 vào biểu thức trên ta được: (6 + 4 -3.30)(6 + 4 + 3.30) = - 80.100 = - 8000 |
0.5đ 0.5đ
0.5đ
0.5đ |
5 |
|
|
1.5đ |
5a |
x3 + x2 – x + a x + 2 x3 + 2x2 x2 - x + 1 - x2 - x + a - x2 - 2x x + a x + 2 a - 2
Để x3 + x2 – x + a x + 2 thì a – 2 = 0 a = 2 |
0.5đ
0.25đ
|
|
5b |
a2 + b2 + c2 = ab + bc + ca a2 + b2 + c2 - ab - bc – ca = 0 2a2 +2 b2 + 2c2 -2 ab - 2bc – 2ca = 0 (a2- 2ab + b2)+( b2 – 2bc + c2)+(c2 – 2ac +a2) = 0 (a – b )2 +( b – c)2 + ( c – a)2 = 0 a – b = 0, b – c = 0, c – a = 0 a= b = c |
0,25đ
0.25đ
0.25đ |
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