福建省福州市2020-2021学年九年级上学期期末质量抽测数学试题（图片版）

九年级数学答案 - 1 - （共 6 页） 2020－2021 学年度第一学期福州市九年级期末质量抽测 数学试题答案及评分标准 评分说明： 1．本解答给出了一种或几种解法供参考，如果考生的解法与本解答不同，可根据试题的主要考 查内容比照评分参考制定相应的评分细则． 2．对于计算题，当考生的解答在某一步出现错误时，如果后继部分的解答未改变该题的内容和 难度，可视影响的程度决定后继部分的给分，但不得超过该部分正确解答应给分数的一半； 如果后继部分的解答有较严重的错误，就不再给分． 3．解答右端所注分数，表示考生正确做到这一步应得的累加分数． 4．只给整数分数．选择题和填空题不给中间分． 一、选择题（共 10 小题，每小题 4 分，满分 40 分；在每小题给出的四个选项中，只有一项是符合题目要求的， 请在答题卡的相应位置填涂） 1．B 2．D 3．B 4．C 5．B 6．D 7．B 8．C 9．A 10．A 二、填空题（共 6 小题，每小题 4 分，满分 24 分，请在答题卡的相应位置作答） 11．3π 12．3 13． 4− ＜y＜ 4 3 − 14． 2 15． 3 8 16．6 6 三、解答题（共 9 小题，满分 86 分，请在答题卡的相应位置作答） 17．（本小题满分 8 分） 解法一： 1a = ， 2b = − ， 1c = − ， ····················································································· 1 分 2 4b acΔ = − 2=( 2) 4 1 ( 1) 8− − × × − = ＞0． ·············································································· 3 分 方程有两个不等的实数根 2 4 2 b b acx a − ± −= ···························································································· 4 分 2 8 1 2 2 =（ ）− − ±= ± ， ···················································································· 6 分 即 1 1+ 2x = ， 2 1 2x = − ． ················································································· 8 分 解法二： 2 2 1x x− = ， ···································································································· 1 分 2 2 1 2x x− + = ， ································································································ 3 分 2( 1) 2x − = ， ···································································································· 4 分 1 2x − = ± ， ··································································································· 6 分 2 1x += ± ， 即 1 2 1x = + ， 2 2 1x = − + ． ·············································································· 8 分 九年级数学答案 - 2 - （共 6 页） 18．（本小题满分 8 分） 证明：连接 OC． ∵AC 平分∠DAB， ∴ DAC CAB∠ = ∠ ． ····························································································· 1 分 ∵ OA OC= ， ∴ OCA CAB∠ = ∠ ， ···