河南安阳市安阳县2019-2020学年八年级下学期期末教学质量检测数学试题（扫描版）

八年级数学答案 第 1 页（共 3 页） 2018—2019 学年第二学期教学质量检测 八年级数学参考答案及评分意见 一、选择题（每小题 3 分，共 30 分） 1．B 2．B 3．B 4．A 5．D 6．C． 7．A 8．A 9．D 10．C 二、填空题（每小题 3 分，共 15 分） 11．166 cm 12．1 13．2 14．12 15． 17 cm 或 2 2 cm 三、解答题（本大题 8 小题，共 75 分） 16．（1）解：原式＝ 2 2 5 3 . ······································································ 2 分 ＝5－3 ··············································································· 3 分 ＝2． ················································································· 4 分 （2）解：原式= 1 2 2 2 6 2 3 4 2 2      ················································· 2 分 = 4 2 3 2 12 2  ····························································· 3 分 =13 2 ． ·········································································· 4 分 17．证明：如图连接 AC 交 EF 于点 O， ··························································· 1 分 ∵ 四边形 ABCD 是平行四边形， ∴ AO=CO， BO=DO． ········································································· 3 分 又 BE = DF， ∴ BO+BE=DO+DF． ∴ EO=FO． ······················································································· 7 分 ∴ 四边形 AECF 是平行四边形． ····························································· 8 分 18．解：（1）将公司 25 名员工月收入数据由小到大排列，处于中间位置的数据为 3000，因 此公司员工月收入中位数为 3000； ··························································· 3 分 （2）用所求平均数反映公司全体员工月收入水平不合适； 这个公司员工月收入平均数为 6080 元，但在 25 名员工中，仅有 3 名员工的收入在平均 数以上，而另有 22 名员工收入在平均数以下，因此，用平均数反映所有员工的月收入 不合适，利用中位数更好． ····································································· 8 分 19．解：（1）令 y＝0 代入解析式可得：x＝4， O B D CF EA 八年级数学答案 第 2 页（共 3 页） 所以 A（4，0）． ··················································································· 2 分 令 x＝0 代入解析式可得：y＝3． 所以 B（0，3）． ··················································································· 4 分 （2）由勾股定理，得 BA= 543 22  ． ············································ 5 分