精彩假期八年级寒假作业答案

一,选择题 
1.B 本题考查的是无理数的计算,平方根的概念,其中⑤学生易判断错,注意进行审题能力的培养
2.D 本题考查位置的确定及平行四边形的中心对称性
3.C 本题考查了对等腰梯形性质的理解及基本图形法的应用,正确的3个分别是A.B.D
4.A 本题考查了一次函数图像的性质,应渗透数形结合思想讲解
5.D 本题考查了二元一次方程组的图像解法,体现了二元一次方程组与一次函数的关系,应渗透数形结合思想
6.C本题考查了旋转变换,结合构造全等的解题技巧
二,填空题 
7.25 本题考查了勾股定理与公式变形,可适当渗透因式分解知识
8.x>–2.7 本题突出数形结合思想,考查了一次函数与不等式的关系
9.1 本题考查了平移变换,平行四边形判定及面积计算,方程思想,观察与猜想能力.
三,解答题 
10.(1)300  (2)1060 (3)15; 
(4)合理.理由中体现用样本估计总体即可.(只答"合理"得1分)
(本题考查了读图,搜集数据,平均数的计算和统计思想的运用)
11.解答:(1) ……   解得:…… 
(2)①当时,;当>120时, …… 
(本题考查了方程组的解法,应用能力及方程及函数思想的综合运用)
12.解:(1)符合条件的点的坐标是D1(0. -1). 
设直线的解析式为,
由题意得 解得 
直线的解析式为. 
(2) 
13.(1)∵CE为∠BCA的内角平分线,∴∠BCE=∠ECA,又∵MN‖BC
∴∠BCE=∠FEC,∴∠FEC=∠BCE ,∴OE=OC,同理OC=OF,所以OE=OF…

(2)当O运动为AC的中点时,四边形AECF是矩形. …………
∵CE,CF分别为∠BCA的内外角平分线,AO=OC,EO=OF,
又∵∠ECF=90°,∴AECF为矩形. …………  
(3)当AC⊥BC,O为AC的中点时,AECF是正方形.…………  
(本题考查了初步的猜想,论证能力,特殊平行四边形的判定及基本图形法的应用)
14.
数学学案2参考答案:
【一试身手】
【基础训练】
1.D
2. B
3.
4. x<-1 .
5.答案:解:(1)y1=元;
y2=元.
(2)当时,解得.
当顾客购物元时,到两家超市购物所付费用相同;
当时,解得,而,.
即顾客购物超过元且不满元时,到乙超市更优惠;
当时,解得,
即当顾客购物超过元时,到甲超市更优惠.
【提高训练】
6. A
7. C
8. 3或一3.
9.解:(1)设购进种商品件,种商品件.
根据题意,得 
化简,得
解之,得 
答:该商场购进两种商品分别为200件和120件. 
(2)由于商品购进400件,获利为(元).
从而商品售完获利应不少于(元).
设商品每件售价为元,则. 
解得.
所以,种商品最低售价为每件1080元. 
10. 答案:(1)x0的解为x0的解为x0的解为x0的解为xy乙,即1.2x+900>1.5x+540∴x<1200
若y甲=y乙,即 1.2x+900=1.5x+540∴x=1200
若y甲当x=2000时,y甲=3300 答:当500≤x1200份时,选择甲厂比较合算;
所以要印2000份录取通知书,应选择甲厂,费用是3300元
提高训练
10.=2或3 11.D
12.设本场比赛特里得了x分,则纳什得分为x+12由题意,得
解得22答:小牛队赢了,特里得了23分,纳什得了35分.
13.解:设饼干的标价每盒x元,牛奶的标价为每袋y元,
则 得8将x=9代入④,得y=9.2-0.9×9=1.1,答:饼干一盒标价9元,一袋牛奶标价1.1元
14.(1) ∵ 用A型车厢节,则B型车厢为(40-)节,得

(2) 依题意,得 ≥
≥ 解之,得 ≤≤
∵ 取整数, ∴ 或或. ∴ 共有三种方案:
① 24节A型车厢和16节B型车厢;
② 25节A型车厢和15节B型车厢;
③ 26节A型车厢和14节B型车厢.
(3) 当时,万元; 当时,万元;
当时,万元;
故安排方案③,即A型车厢26节,B型车厢14节最省,最省费用为26.8万元.
初二英语学案一 答案
I. BDAAD, CCAAB, BABAD, CACDC, ADBCC, CCAAC
II. ABDCD, ADCBA
III. CADDD, FFTFT
IV. 1. astronaut 2. buildings 3. pets 4. failed 5. loud
6. pollution 7. less 8. fewer 9. boring 10. styles
V. 1. sale 2. plays 3. prediction 4. Teaching 5. (to) take
6. to study 7. laughing 8. swimming 9. planning 10. cut
11. won't be 12. will work 13. flew 14. skating 15. myself
VI. 1. won't study 2. Will there, any 3. Where will 4. How soon will
5. have time 6. What is 7. unexpensive 8. didn't lose
9. I spent, on 10. don't, should 11. What's the matter 12. will play
13. doesn't have any, either 14. What will, do
VII. 1. in the future 2. hundreds of years 3. As, will meet lots of
4. plays, loud 5. are out of style 6. to talk about, on the phone
7. enough food 8. left, at school 9. On the other hand
10. never asks, for 11. shouldn't argue with 12. called me up
13. will fly, to 14. will, be like in 15. which, will win, World Cup
16. agree with 17. Keeping healthy 18. seems, waiting for
19. hope, will come true , future 20. It's impossible for me
VIII. 1. D in two days 2. D the funniest 3. B be 4. C much 5. B write
6. C sing 7. A borrow 8. D except 9. D advice 10. C much
11. C surprise 12. D pay for 13. D for 14. in 15. B was
IX. A. 1. keep out 2. looking for 3. paid for 4. found out 5. left out
6.comfortable 7. loud 8.advice 9. original 10. important
B. 1. need 2. have learned/ have learnt 3. made 4.am trying
5. will / am going to improve 6. to know 7. helping
初二英语学案2参考答案
Unit3 单元过关直通车答案:
I. 1. flight 2. heroes 3. was reading, came 4. jumped, was moving
5. was cooking, was washing 6. were having 7. rode 8. was looking
9. were walking 10. Silence 11. arrived 12. won't do 13. reading, listen
14. Was, lying 15. were watching 16. was, sleeping, got 17. was cooking, was washing
18. was driving, rained 19. will be 20. was shopping
II. 1—5: BCAAC 6---10: DBBAB 11---15: ADACC 16---20: BBAAC 21---25: CBDCD
III. 1. doesn't do 2. didn't leave, until 3. while, was watching 4. the best basketball player / the best at basketball 5. isn't he 6. What was, doing, you 7. Isn't it
IV. 1. one of the best teachers 2. muder took place on 3. while, was listening 4. to get out of
5. had an unusual experience
V. A ended, was, was walking, heard, was following, was, began, said, was, came
B. 1. studying 2. Among 3. seem 4. believe 5. earth 6. back 7. Maybe 8. balloon 9. understand 10. answer
VI. 1---5: CBDAD 6----10: AABCB
VII. 1---5: BDABD
初二数学第4讲参考答案:
【一试身手】
【基础练习】
1.()
2.把下列多项式分解因式:
(1) (2) (3)

(4) (5 )

3. (答案略)
4.答案:能,bn+bm+am+an=(a+b)(m+n)
5.答案:a2-4b2=(a+2b)(a-2b)=(13.2+2×3.4)(13.2-2×3.4)=20×6.4=128
6.(1)答案:x3y-2x2y2+xy3=xy(x-y)2=2×12=2
(2)答案:化简a(a-1)-(a2-b)=1,得b-a=1,
==
7.(1);
(2).
(3)
【提高练习】
8.(n+11)2-n2=11(2n+11),得证
9.答案:4x,-4x,
10.答案:,当x=-1时,能取最小值,最小值为1
11.答案:
所以x=-2,y=5,所以=xy(x+y)=-10×3=-30
12. 答案:两个连续奇数的平方差是8的倍数
设两个连续奇数分别为(2k+1)和(2k-1),则
(2k+1)2-(2k-1)2=[(2k+1)+(2k-1)] [(2k+1)-(2k-1)]=8k
初二英语学案3答案:
一,选择填空
1-5 CDAAD 6-10 ABDCA 11~15 BBBBB 16~20 AABAA
二,用所给词的适当形式填空.
1. First 2. supposed 3. healthy 4. Lucky 5. worse
6. chose 7. Asians 8. speakers 9. report cards 10. copies
三,完形填空
1~5 BBCDC 6~10 DACCD
四,阅读理解
1-5 DDACB
1.taught the younger members everything they knew
2.invented letters and learned how to write
3.specialized job
4.Egypt and perhaps in China about 5 or 6 thousand years ago
5.the right of every child
五,选词填空
useful, life, much, out, in, families, for, improve, use, complain, behind, other, themselves
完成句子:
although, well in, am bad
take me, reply to
first, thin, feel sick
really hard time with
fact, few differences between
opened up, start in
初二物理浮力(二)答案
巩固练习(一)
1.A 2.C 3.不变,变大 4.等于,等于 5.C 6.D 7.C 8.B 9.D 10.D
巩固练习(二)
1. 0.9×103kg/m3 2.A 3.变小,不变 4.9V/4 5.3/4,等于 6.2∶3 7. 4∶3 8.C
巩固练习(三)
1.7.4N 2. 1.5×103kg/m3 3.D 4.F浮=8N, V物=8×10-4kg/m3 ρ物=1.25×103kg/m3 5.m=2kg, ρ=2.0×103kg/m3 6. 8∶9 7.(1)2.00, 2.50 , 2.50 , 2.50 (2)略 (3)圆柱形物体在浸没液面之前所受浮力跟浸入液体的深度成正比;在浸没液面以后所受浮力不变.8.(1)300N, (2)100N. 9.(1)0.35kg (2) 2×10-4kg/m3 (3) 聚偏二氟乙烯
巩固练习(四)
1.(1)所处深度(2)乙,丁或丙,丁 2.D 3.(1)用刻度尺测出木块的边长a,(2)让木块漂浮在水面上,测出木块浸入水中的深度h,(3)木块密度ρ=hρ水/a 4.(1) 让木块漂浮在水面上,测出木块浸入水中的深度h1, (2)再让木块漂浮在盐水面上,测出木块浸入盐水的深度h2,(3)ρ盐水=h1ρ水/h2 5.(1)用细线拴住石块挂在弹簧测力计下测出重力G,(2)再让石块浸没在水中读出此时的拉力F,(3)石块密度ρ石=Gρ水/(G-F) 6. (1)用细线拴住石块挂在弹簧测力计下测出重力G,(2)再让石块浸没在水中读出此时的拉力F1,(3) 再让石块浸没在盐水中读出此时的拉力F2,(4)盐水密度ρ盐水=(G-F2)ρ水/(G-F1)
7.(1)器材:弹簧测力计,茶杯,水,线绳,石块.实验步骤:①用细线拴住石块挂在弹簧测力计下测出重力G,②再让石块浸没在水中读出此时的拉力F1,③再让石块浸没在牛奶中读出此时的拉力F2,④牛奶密度ρ牛奶=(G-F2)ρ水/(G-F1) (2)线绳要细,所取石块尽可能大些,从水中取出石块后将水擦干再放入牛奶中.8.步骤:(1)在量筒中注入适量的水并读出水的体积V1,(2)让酒盅漂浮在量筒里的水面上,读出水面对应的体积值V2,(3)让酒盅浸没在水面下,读出水面对应的体积值V3 .酒盅密度表达式ρ=(V2-V1)ρ水/(V3-V1)