甘肃省兰州市2019届九年级4月诊断考试数学试题（扫描版）

九年级诊断数学答案第 1页（共 6页） 2019 年兰州市九年级诊断考试 数学参考答案及评分参考 本答案仅供参考，阅卷时会制定具体的评分细则和评分标准。 一、选择题：本大题共 12 小题，每小题 4 分，共 48 分. 题号 1 2 3 4 5 6 7 8 9 10 11 12 答案 C D B C C A B A D A D C 二、填空题：本大题共 4小题，每小题 4 分，共 16 分. 13．x(y＋2)(y－2) 14．65° 15．－4 16． 8 3 π－2 3 三、解答题：本大题共 12 小题，共 86 分．解答时，应写出必要的文字说明、证明过程或 演算步骤. 17．(5分) 解：原式＝4 3 2  ＋ 1－2 3－1，············································································1，2，3，4分 ＝0．································································································································5分 18．(5分) 解：3x2－1＝2x＋2， 3x2－2x－3＝0．·····················································································································1分 ∵a＝3，b＝－2，c＝－3，··································································································2分 △＝（－2）2－4×3×（－3）＝40．················································································ 3分 ∴x 2 1 10 2 3 40 3    ＝ ＝ ．····································································································· 4分 ∴x1 1 10 3 ＋ ＝ ，x2 1 10 3  ＝ ．······························································································5分 19．(5分) 解：原式 2 2 2 1 2 1 1 a a a a a a  － ＋ ＝ － ＋ － ，································································································1分      22 1 1 1 1 a aa a a a a  ＋－ ＝ － ＋ ＋ － ，······················································································ 2分 2 1a ＝ ＋ － 2 1 a a ＋ ＋ ，············································································································ 3分 1 a a ＝－ ＋ ．····················································································································· 4分 当 a＝2时，原式 2 3 ＝－ ．···································································································· 5分 九年级诊断数学答案第 2页（共 6页） 20．(6分) 解：∵AB∥CD，∴∠BEC＝180°－∠B＝180°－96°＝84°．·········································2分 ∵EF平分∠BEC，∴∠BEF＝ 1 2 ∠BEC＝ 1