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1、北师大版八年级下册数学资源与评价答案第一章 一元一次不等式和一元一次不等式组 1(1 不等关系 1(B; 2(A; 3(D; 4(C; 5(C ;6(D;7(1),，(2),;8(3y，4x,0;9(xll(7，x?11(7;1112210(a,1;11(8;12(a，b,ab (a?b) ( a22113(1)2aa+3，(2)，(3)3x，l, 2x,5( y,502214(1)设这个数为x，则x?0;(2)设某天的气温为x?， 则?25( 15(2aa，b,3b( 16(a,b( 17(设参加春游的同学x人，则8x250，9x,250(或8x 250,9x)( 18(50，(20,3)x
2、,270( 19(设该同学至少应答对x道题，依题意有6x,(16,x)260( ,2220(1),(2),(3),(4),(5),; ?2ab(当a,b时取等号)( ab，聚沙成塔:甲同学说的意思是:如果每5人一组玩一个篮球，那么玩球的人数少于50人，有些同学就没有球玩( 乙同学说的意思是:如果每6人一组玩一个篮球，那么就会有一个组玩篮球的人数不足6人( 丙同学说的意思是:如果每6人一组玩一个篮球，除了一个球以外，剩下的每6人玩一个球，还有几个(不足6人)玩另外一个篮球( 1(2 不等式的基本性质 1(C; 2(D; 3(B; 4(A; 5(C; 6(A; 7(C; 8(D; 9(1),(2)
3、,(3),(4),(5),(6),;10(1),(2),(3),(4),;11(a,0; 12(4); 3b13(0，1，2，3，4，5; 14(,; 15(,2 ,0; 16(,( a217x,17(1)x,5;(2);(3)得x,3(4)x,8( 218(解:根据不等式基本性质3，两边都乘以,12，得3a,4a( 根据不等式基本性质1，两边都减去3a，得0,a ，即a0 ，即a为负数( 19(1)a,0;(2)a,l或a,0;(3)a0( 聚沙成塔 511111511.251解:?=(10，)=12(5，,13 41111411111111B441111111.33， =(10，)=13(
4、33，,13 33111111111A11 ?,0 ?A,B AB点拨:利用倒数比较大小是一种重要方法( 1(3 不等式的解集 1(A;2(B;3(C;4(D;5(B;6(A;7(B;8(C;9(答案不唯一，如x,1?0，2x?2等( 10(,55，? (11(x,2( 12(x,1，2，3 13(,6( 14(1)x,3;(2)x,6;(3)x,5;(4)x,2210( 15(x,1，2 16(n,75% 40%?n?49% n,20, 温饱( surface 5mm10MM level markers. (3) protective cover on the pothole point,
5、protection cover and top surface is flush. 10.5.4 thermometer (1) location of embedded two reinforcing 12 and a horizontal 12 embedded reinforcing steel spot welding to secure the thermometer. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped around a three-tier thermo
6、meter key in case the instrument from touch damage and on black cloth fixed to the horizontal bar. (3) when concrete material from the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fill around get rid of 8cm aggregate particle size mixed . (1) joint meter
7、 apart from the extension Rod hook and outside joint flange, all wrapped with a plastic cloth and coated asphalt. (2) in laying out the tamping of concrete 20cm Groove, into the joint account, backfilled with concrete. 10.5.8多 displacement meter (1) according to the design of measuring depth, anchor
8、, a displacement passed rod, pipe, isolation bracket and sensor Assembly and shipped to the laying of venue. (2) assemble multiple point Rod extensometer baled paragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works color 17(图略(18(答案不惟一:(1)x,4; (2) ,3x
9、?1( 19(不少于1.5克( 20(x可取一切实数( 21(非负整数为0，1，2，3( 1222( x,( 523( k大于36时b为负数( 24( a=,3 聚沙成塔 x,y,2x,解:设白球有x个，红球有y个，由题意，得 ,2x，3y,60,由第一个不等式得:3x,3y,6x，由第二个不等式得，3y=60,2x，则有3x,60,2x,6x ?7.5,x,12，?x可取8，9，10，11( 又?2x=60,3y=3(20,y) ?2x应是3的倍数 60,2，9?x只能取9，y = = 14 3答:白球有9个，红球有14个( 1(4一元一次不等式(1) 1(B;2(C;3(D;4(B;5(B
10、;6(D;7(A;8(A;9(x,0，,1，,2，,3，,4 ;10(x,3;1111(R,3;12(,6;13(2;14(2?a,3; 15(x?( 9步错误，应该改成无论x取何值，该不等式总是成立的，所以x取一切数( 16(第?17(1)得x?1;(2)x,5;(3)x?1;(4)x, 3; 231xx，718(1)解不等式,0，得x, 2347231xx，,所以当x,时，的值是非负数( 234231xx，1,1x, (2)解不等式，得 2341231xx，,x,所以当时，代数式的值不大于1 23419(p,6( 20(,11( 聚沙成塔 解:假设存在符合条件的整数m( m,5x,2，mx
11、,由 解得 x，1,232x9,m3xx9,1，,，由 整理得 ， mmmmm9,mm,0x,当时，( 2m,59,m,根据题意，得 解得 m=7 22x,2，mx,1x，1,把m=7代入两已知不等式，都解得解集为，因此存在整数m，使关于x的不等式与3x,1是同解不等式，且解集为( 2rtensometer baled paragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works coloassed rod, pipe, isolation brac
12、ket and sensor Assembly and shipped to the laying of venue. (2) assemble multiple point Rod exdisplacement meter (1) according to the design of measuring depth, anchor, a displacement p 多ount, backfilled with concrete. 10.5.8ll wrapped with a plastic cloth and coated asphalt. (2) in laying out the t
13、amping of concrete 20cm Groove, into the joint accnge, aound get rid of 8cm aggregate particle size mixed . (1) joint meter apart from the extension Rod hook and outside joint flaconcrete material from the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fil
14、l artier thermometer key in case the instrument from touch damage and on black cloth fixed to the horizontal bar. (3) when -nd a threespot welding to secure the thermometer. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped arou thermometer (1) location of embedded two
15、 reinforcing 12 and a horizontal 12 embedded reinforcing steelsurface 5mm10MM level markers. (3) protective cover on the pothole point, protection cover and top surface is flush. 10.5.4 1(4一元一次不等式(2) 1(B; 2(B; 3(C; 4(C; 5(D; 6(12; 7(13; 8(152( 9(以后6天内平均每天至少要挖土80立方米( 10(以后每个月至少要生产100台( 11(不少于16千米( 12
16、(每天至少安排3个小组( 13(招聘A工种工人为50人时，可使每月所付的工资最少，此时每月工资为130000元( 14(甲厂每天处理垃圾至少需要6小时( 15(1)y=9.2,0.9x;(2)饼干和牛奶的标价分别为2元、8元( 聚沙成塔 解:(1)由题意，可将一、二、三等奖的奖品定为相册、笔记本、钢笔即可(此时所需费用为56+105+254,180(元); (2)设三等奖的奖品单价为x元，则二等奖奖品单价应为4x元，一等奖奖品单价为20x元，由题意应由520x，104x，25x?1000，解得x?6.06(元)(故x可取6元、5元、4元(故4x依次应为24元，20元，16元，20x依次应为12
17、0元、100元、80元(再看表格中所提供各类奖品单价可知，120元、24元、6元以及80元、16元、4元这两种情况适合题意，故有两种购买方案，方案一:奖品单价依次为120元、24元、6元，所需费用为990元;方案二:奖品单价依次为80元、16元、4元，所需费用为660元(从而可知花费最多的一种方案需990元( 1(5一元一次不等式与一次函数(1) 41(A;2(D;3(C;4(C;5(B;6(A;7(D;8(B;9(m,4且m?1;10(20;11(x,，x54,;12(x,5;13(x,2;14(x,3;15(,3，0);16(2，3)( 5117(1) x,;(2)x?0( 218( (1
18、)P(1，0);(2)当x,1时y,y，当x,1时y,y( 1212聚沙成塔 在直角坐标系画出直线x,3，x，y,0，x,y，5,0， 因原点(0，0)不在直线x,y，5,0上， 故将原点(0，0)代入x,y，5可知，原点所在平面区域表示x,y+5?0部分， 因原点在直线x+y=0上， 故取点(0，1)代入x+y判定可知点(0，1)所在平面区域表示x+y?0的部分，见图阴影部分( 1(5 一元一次不等式与一次函数(2) 1(B;2(B;3(A;4(13; 5(1)y=600+500x y=2000+200x; 122(2)x,4，到第5个月甲的存款额超过乙的存款额( 36(设商场投入资金x元，
19、 3aragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works colorsolation bracket and sensor Assembly and shipped to the laying of venue. (2) assemble multiple point Rod extensometer baled pdisplacement meter (1) according to the design of measuring depth
20、, anchor, a displacement passed rod, pipe, i 多ith concrete. 10.5.8plastic cloth and coated asphalt. (2) in laying out the tamping of concrete 20cm Groove, into the joint account, backfilled with a m aggregate particle size mixed . (1) joint meter apart from the extension Rod hook and outside joint f
21、lange, all wrapped wfrom the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fill around get rid of 8cte material tier thermometer key in case the instrument from touch damage and on black cloth fixed to the horizontal bar. (3) when concre-ecure the thermom
22、eter. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped around a threethermometer (1) location of embedded two reinforcing 12 and a horizontal 12 embedded reinforcing steel spot welding to ssurface 5mm10MM level markers. (3) protective cover on the pothole point, prote
23、ction cover and top surface is flush. 10.5.4 如果本月初出售，到下月初可获利y元， 1则y,10%x，(1，10%)x?10%,0.1x，0.11x,0.21x; 1如果下月初出售，可获利y元，则y,25%x,8000,0.25x,8000 22当y,y即0.21x,0.25x,8000时，x,200000 12当y,y即0.21x,0.25x,8000时，x,200000 12当y,y即0.21x,0.25x,8000时，x,200000 12? 若商场投入资金20万元，两种销售方式获利相同;若商场投入资金少于20万元，本月初出售获利较多，若投入资
24、金多于20万元，下月初出售获利较多( 7(1)分两种情况:y=x(0?x?8)，y=2x,8(x,8); (2)14( 138(1)乙在甲前面12米;(2)s,8t，s,12，t; 甲乙2(3)由图像可看出，在时间t,8秒时，甲走在乙前面，在0到8秒之间，甲走在乙的后面，在8秒时他们相遇( 9(解:如果购买电脑不超过11台，很明显乙公司有优惠，而甲公司没优惠，因此选择乙公司(如果购买电脑多于10台(则:设学校需购置电脑x台，则到甲公司购买需付105800，5800(x,10)70%元，到乙公司购买需付580085% x元(根据题意得: 1)若甲公司优惠:则 105800，5800(x,10)7
25、0%,580085% x 解得: x,20 2)若乙公司优惠:则 105800，5800(x,10)70%,580085% x ,20 解得: x3)若两公司一样优惠:则 105800，5800(x,10)70%,580085% x 解得: x,20 答:购置电脑少于20台时选乙公司较优惠，购置电脑正好20台时两公司随便选哪家，购置电脑多于20台时选甲公司较优惠( 10(1)他继续在A窗口排队所花的时间为 aa,，,428(分) ,44(2)由题意，得 aa,，,，426252，解得 a,20( ,4611( 解:(1)设轿车要购买x辆，那么面包车要购买(10,x)辆，由题意得: 7x，4(1
26、0,x)?55 解得:x?5 又?x?3，则 x,3，4，5 ?购机方案有三种: 方案一:轿车3辆，面包车7辆;方案二:轿车4辆，面包车6辆;方案三:轿车5辆，面包车5辆; (2)方案一的日租金为:3200，7110,1370(元) 方案二的日租金为:4200，6110,1460(元) 方案三的日租金为:5200，5110,1550(元) 为保证日租金不低于1500元，应选择方案三( 12(1)y,50，0.4x，y,0.6x; 12(2)当y,y，即50，0.4x,0.6x时，x,250(分钟)，即当通话时间为250分钟时，两种通讯方式12的费用相同; (3)由y,y即50，0.4x,0.6
27、x，知x,250，即通话时间超过250分钟时用“全球通”的通讯方式便宜( 124rtensometer baled paragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works coloassed rod, pipe, isolation bracket and sensor Assembly and shipped to the laying of venue. (2) assemble multiple point Rod exdisplacem
28、ent meter (1) according to the design of measuring depth, anchor, a displacement p 多ount, backfilled with concrete. 10.5.8ll wrapped with a plastic cloth and coated asphalt. (2) in laying out the tamping of concrete 20cm Groove, into the joint accnge, aound get rid of 8cm aggregate particle size mix
29、ed . (1) joint meter apart from the extension Rod hook and outside joint flaconcrete material from the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fill artier thermometer key in case the instrument from touch damage and on black cloth fixed to the horiz
30、ontal bar. (3) when -nd a threespot welding to secure the thermometer. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped arou thermometer (1) location of embedded two reinforcing 12 and a horizontal 12 embedded reinforcing steelsurface 5mm10MM level markers. (3) protec
31、tive cover on the pothole point, protection cover and top surface is flush. 10.5.4 13(解:(1)该商场分别购进A、B两种商品200件、120件( (2)B种商品最低售价为每件1080元( 聚沙成塔 解:(1)500n; (2)每亩年利润,(14004，16020),(500，754，5254，1520，8520) ,3900(元) (3)n亩水田总收益,3900n 需要贷款数,(500，754，5254，1520，8520)n,25000,4900n,25000 ,(4900n,25000),392n,200
32、0 贷款利息,8根据题意得: 3900n,(392n,2000),35000解得:n?9.41 ? n ,10 需要贷款数:4900n,25000,24000(元) 答:李大爷应该租10亩水面，并向银行贷款24000元，可使年利润超过35000元( 1(6 一元一次不等式组(1) 1(C;2(D;3(C;4(C;5(A;6(D;7(D;8(,1,y,2;9(,1?x,3; 110(,?x?4;11(M?2;12(2?x,5;13(a?2;14(,6;15(A?1; 43101,x16(1);(2)无解;(3),2?x,;(4)x,3( 3235,x，3，整数解为2，1，0，,1( 17(解集为
33、42718(不等式组的解集是，所以整数x为0( ,x31069x,19(不等式组的解集为， 所以不等式组的非负整数解为:0，l，2，3，4，5( 13聚沙成塔 ,4,m,0.5( 1(6(一元一次不等式组(2) 1(解:设甲地到乙地的路程大约是xkm，据题意，得 1610+1.2(x,5)?17.2， 解之，得10,x?11， 即从甲地到乙地路程大于10km，小于或等于11km( 2(解:设甲种玩具为x件，则甲种玩具为(50,x)件(根据题意得: 80x，100(50,x),4600, ,140x，120(50,x),6440,解得:20?x?22 答:甲种玩具不少于20个，不超过22个( 3
34、(1)y,3.2,0.2x (2)共有三种方案，A、B两种车厢的节数分别为24节、16节或25节、15节或26节、14节( 4(1)共有三种购买方案，A、B两种型号的设备分别为0台、10台或1台、9台或2台、8台;(2)A、B两种型号的设备分别1台、9台;(3)10年节约资金42.8万元( 5(解:设明年可生产产品x件，根据题意得: 5aragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works colorsolation bracket and se
35、nsor Assembly and shipped to the laying of venue. (2) assemble multiple point Rod extensometer baled pdisplacement meter (1) according to the design of measuring depth, anchor, a displacement passed rod, pipe, i 多ith concrete. 10.5.8plastic cloth and coated asphalt. (2) in laying out the tamping of
36、concrete 20cm Groove, into the joint account, backfilled with a m aggregate particle size mixed . (1) joint meter apart from the extension Rod hook and outside joint flange, all wrapped wfrom the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fill around g
37、et rid of 8cte material tier thermometer key in case the instrument from touch damage and on black cloth fixed to the horizontal bar. (3) when concre-ecure the thermometer. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped around a threethermometer (1) location of embe
38、dded two reinforcing 12 and a horizontal 12 embedded reinforcing steel spot welding to ssurface 5mm10MM level markers. (3) protective cover on the pothole point, protection cover and top surface is flush. 10.5.4 120x,800，2400,10000,x,12000 解得:10000?x?12000 ,4x,6000，60000,答:明年产品至多能生产12000件( 6(解:设宾馆底层
39、有客房x间，则二楼有客房(x+5)间(根据题意得: 4x,48,5x,48, 解得:9.6,x,11，所以 x = 10 ,3(x，5),48,4(x，5),48,答:该宾馆底层有客房10间( ,，x407(解:(1) yxx,，,32(20)(2)由题意可得 203(20)264xx，,? ?, ,486(20)708xx，,? ?,解?得x?12 解?得x?14 ?不等式的解为12?x?14 ?x是正整数 13，14 ?x的取值为12，即有3种修建方案:?A型12个，B型8个;?A型13个，B型7个;?A型14个，B型6个( (3)?y,x，40中，随的增加而增加，要使费用最少，则x,12
40、 yx?最少费用为y,x，40,52(万元) 村民每户集资700元与政府补助共计:700264，340000,524800,520000 ?每户集资700元能满足所需要费用最少的修建方案( 8(解:(1)设一盒“福娃”元，一枚徽章y元，根据题意得 x2315xy，,x,150, 解得 ,y,15xy，,3195,答:一盒“福娃”150元，一枚徽章15元( (2)设二等奖m名，则三等奖(10m)名， 216515015(10)1000，,mm?, ,216515015(10)1100，,mm?,104124?m解得( 2727?m是整数，?m,4，?10,m,6( 答:二等奖4名，三等奖6名(
41、单元综合评价 11( 3a,2b?5; 2(0，1，2，3; 3( ,; 4( x,; 5( m,2; 6(,人或,人; 26rtensometer baled paragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works coloassed rod, pipe, isolation bracket and sensor Assembly and shipped to the laying of venue. (2) assemble multipl
42、e point Rod exdisplacement meter (1) according to the design of measuring depth, anchor, a displacement p 多ount, backfilled with concrete. 10.5.8ll wrapped with a plastic cloth and coated asphalt. (2) in laying out the tamping of concrete 20cm Groove, into the joint accnge, aound get rid of 8cm aggr
43、egate particle size mixed . (1) joint meter apart from the extension Rod hook and outside joint flaconcrete material from the equipment above 1.5M, vibrators shall not close within 1.0M; the system of artificial back fill artier thermometer key in case the instrument from touch damage and on black c
44、loth fixed to the horizontal bar. (3) when -nd a threespot welding to secure the thermometer. (2) when the concrete surface to planted around 20cm, with a black cloth wrapped arou thermometer (1) location of embedded two reinforcing 12 and a horizontal 12 embedded reinforcing steelsurface 5mm10MM le
45、vel markers. (3) protective cover on the pothole point, protection cover and top surface is flush. 10.5.4 a，1x7( ; 8( ; 9(x,2; 10( 1( x,4a,511( D; 12( B;13( B;14( C;15( D;16( C;17( B;18( A( 19(解:图略 (1)x,4 (2),6?x?,2( 20(1)x?4;(2)x,3;(3)1,x?2; (4)2,x?4( 2221( 解:9a + 5a + 3,(9a,a ,1),6a，4 222当6a，4,0即a
46、,时，9a + 5a + 3,9a,a ,1 3222当6a，4,0即a,时，9a + 5a + 3,9a,a ,1 3222当6a，4,0即a,时，9a + 5a + 3,9a,a ,1( 322(解:根据三角形三边关系定理，得 1,2a,8，3, ,1,2a,8,3,5,a,2 解得 ( 23(解:设导火线至少需xcm，根据题意，得 x 5,402 1x,80.4 x,81 答:导火线至少需要81厘米长( 24(解:假设存在符合条件的整数m( m,5x,2，mx,由 解得 x，1,232x9,m3xx9,由 整理得 ， 1，,，mmmmm9,mm,0x,当时，( 2m,59,m,根据题意，
47、得 解得 m=7 22x,1把m=7代入两已知不等式，都解得解集为 x,2，mx,1x，1,因此存在整数m，使关于x的不等式与是同解不等式，且解集为( 325(解:(1)y=250x+200，y=222x+1600( 12(2)分三种情况:?若y,y，250x+200,222x+1600，解得x,50; 12?若y=y，解得x=50; 12?若y,y，解得x,50( 12因此，当所运海产品不少于30吨且不足50吨时，应选择汽车货运公司承担运输业务;当所运海产品刚好50吨时，可选择任意一家货运公司;当所运海产品多于50吨时，应选择铁路货运公司承担业务( 第二章 分解因式 2.1分解因式 m,1,n,21.整式，积;2.整式乘法;3.因式分解;4.C;5.A;6.D;7.D;8.B;9.; 7aragraph by paragraph and Grouting pipes, pipe joints sealed with glue, and make a logo designer works colorsolation bracket and sensor Assembly and shipped to the laying of venue. (2) assemble multiple point Ro