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《山西省2018-2019学年第二学期八年级阶段三质量评估试题·数学(北师版)·答案.pdf》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、19.解:(1)如图所示,点D即为所求.山西省2018-2019学年第二学期八年级阶段三质量评估试题数学(北师版)参考答案和评分标准!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!3分一、选择题(每小题3分,共30分)(2)如图,连接AD,!!!!!!!!!!!!!!!!!!!!!!!!4分题号12345678910∵△ABC中,∠C=90°,∠B=37°,选项DBCCABADCB∴∠BAC=90°-37°=53°.!!!!!!!!!!!!!!!!!!!!!!!5分∵AD=BD,二、填空题(每小题3分,共15分)∴∠B=∠BAD=37°,!!!!!!!!!!!!!
2、!!!!!!!!!!!6分12-姨211.2x(x+2)(x-2)12.3513.90°14.提公因式法15.或∴∠CAD=∠BAC-∠BAD=53°-37°=16°.!!!!!!!!!!!!!!!7分22432220.解:(1)a-4ab+4ab三、解答题(本大题共8小题,共75分)222=a(a-4ab+4b)!!!!!!!!!!!!!!!!!!!!!!!!!!1分2216.解:(1)原式=-5x(x-2xy+y)!!!!!!!!!!!!!!!!!!!!!4分22=a(a-2b).!!!!!!!!!!!!!!!!!!!!!!!!!!!!2分2=-5x(x-y).!!!!!!!!
3、!!!!!!!!!!!!!!!5分1(2)原式=a(2a-b)-9b(2a-b)!!!!!!!!!!!!!!!!!!!!!!8分当a=-1,b=时,222=(a-b)(a-9b)!!!!!!!!!!!!!!!!!!!!!!!9分122原式=(-1)×∠-1-2×∠!!!!!!!!!!!!!!!!!!!!!!3分=(a-b)(a+3b)(a-3b).!!!!!!!!!!!!!!!!!!!10分22≤2x-15x+1=1×(-1-1)≤-≤1,①≤≤3217.解:≤=4.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!4分≤≤≤≤5x-1<3(x+1).②113223(2)a
4、b-ab+ab解不等式①,得x≥-1,!!!!!!!!!!!!!!!!!!!!!!!2分22解不等式②,得x<2.!!!!!!!!!!!!!!!!!!!!!!!!4分=1ab(a2-2ab+b2)!!!!!!!!!!!!!!!!!!!!!!!!!5分2∴不等式组的解集为-1≤x<2.!!!!!!!!!!!!!!!!!!!5分12在数轴上表示不等式组的解集为:=ab(a-b).!!!!!!!!!!!!!!!!!!!!!!!!!!!6分2当a-b=2,ab=8时,12原式=×8×2!!!!!!!!!!!!!!!!!!!!!!!!!!7分!!!!!!!!!!!!!!!!!!!!!!!!!
5、!!!!!!!!7分218.解:(1)C!!!!!!!!!!!!!!!!!!!!!!!!!!!!!3分=16.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!8分421.%解:(1)a2-b2=(a+b)(a-b)!!!!!!!!!!!!!!!!!!!!!!3分(2)(x-3)!!!!!!!!!!!!!!!!!!!!!!!!!!!!6分(3)设x2-2x=y.!!!!!!!!!!!!!!!!!!!!!!!!!!7分(2)由题意可得:a-b=3.!!!!!!!!!!!!!!!!!!!!!!!4分22原式=y(y+2)+1!!!!!!!!!!!!!!!!!!!!!!!!!!8
6、分∵a-b=(a+b)(a-b)=57.=y2+2y+1∴a+b=19.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!6分=(y+1)2!!!!!!!!!!!!!!!!!!!!!!!!!!!9分a+b=19,a=11,∴∠解得∠!!!!!!!!!!!!!!!!!!!!!!8分=(x2-2x+1)2a-b=3.b=8.=(x-1)4.!!!!!!!!!!!!!!!!!!!!!!!!!!10分∴a,b的值分别是11,8.!!!!!!!!!!!!!!!!!!!!!!!9分八年级数学答案(北师版)第1页(共3页)八年级数学答案(北师版)第2页(共3页)222.解:(1)(x-3
7、)-1!!!!!!!!!!!!!!!!!!!!!!!!!!2分2(2)①x+2x-32=x+2x+1-1-3!!!!!!!!!!!!!!!!!!!!!!!!!!!3分2=(x+1)-4!!!!!!!!!!!!!!!!!!!!!!!!!!!!!4分=(x+1+2)(x+1-2)!!!!!!!!!!!!!!!!!!!!!!!!!5分=(x+3)(x-1).!!!!!!!!!!!!!!!!!!!!!!!!!!!6分2②4x+12x-7222=(2x)+12x+3-3-7!!
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