辽宁省锦州市2020-2021学年八年级上学期期末质量检测数学试题（PDF版）

八年级数学答案第 1 页（共 6 页） 2020—2021 学年度八年级（上）期末质量检测 数学试题参考答案及评分标准 注：若有其他正确答案请参照此标准赋分. 一、选择题（本题共 8 个小题,每小题 2 分，共 16 分） 题号 1 2 3 4 5 6 7 8 选项 D B C B D A D C 二、填空题（本题共 8 个小题,每小题 2 分，共 16 分） 9． 10．y1<y2（或 y2 > y1） 11．（3，150°） 12．丙 13．94.2 14． 或 15． 16．2 2020 三、解答题（本题共 3 个小题，每小题 5 分，共 15 分） 17.（1）解:原式＝2 ﹣5× + ···················································· 3 分 ＝2 ﹣ + ······················································· 4 分 ＝ .······································································· 5 分 说明：第一步共 3 分，其中化简 正确给 2 分，化简 正确给 1 分， 第二步化简 5× 正确给 1 分. （2）解：原式＝2+2 2 +1+3﹣4····························································· 4 分 ＝2+2 2 . ··········································································· 5 分 说明：化简 给 2 分，化简 给 2 分. （3） 解：方法 1：①×3+②，得 7x＝14. ····················································· 1 分 解得 x＝2. ··············································································· 2 分 把 x＝2 代入①，得 2﹣y＝3. ······················································· 3 分 解得 y＝﹣1． ········································································· 4 分 八年级数学答案第 2 页（共 6 页） 第 18 题图 成绩/分 人数（频数） 12 10 8 6 4 2 0 98 94 90 86 82 78 所以方程组的解为      .1 ,2 y x ······················································· 5 分 方法 2：由①，得 x＝y+3 ③. ···························································· 1 分 将③代入②, 得 4(y+3)+3y＝5. ·················································· 2 分 y＝﹣1． ·························································· 3 分 将 y＝﹣1 代入③，得 x＝2. ························································ 4 分 所以方程组的解为      .1 ,2 y x ······················································· 5 分 四、解答题（本大题共 3 个题，第 18，19 题各 6 分，第 20 题 7 分，共 19 分） 18．（1）5， 6. ····································································· （各 1 分）2 分 （2）补充的频数直方图如图所示： ····················································· 4 分