江苏省徐州市市区2020-2021学年九年级上学期期中检测数学【试卷答案】.doc

2 2 2 1 2 BC2020-2021 学年度第一学期期中检测 九年级数学试题参考答案及评分标准题号选项1C2A3B4A5C6B7D8B9．－2 10． k <14且k ¹011．2 12． y =( x -1) +113．1 或 4 14．55 15．917．2 18 ． -85416． 2 319．（1）原式=1－2+3－4（4 分）=－2； · ························································· 5 分（2）∵a=2，b=－1，c=－3， b -4 ac =( -1) -4 ´2 ´( -3) =25 >0 ；（2 分）∴ x =1 ± 25 1 ±5 3= ，（3 分）即 x =-1, x = ·································· 5 分 2 ´2 4 2（其他方法，如因式分解法、配方法酌情给分）20．（1）∵四边形 ABCD 内接于⊙O，∴∠BAD+∠BCD=180°， ··························· 1 分 ∴∠BCD=180°－∠BAD=180°－105°=75°， ····································· 2 分 而 ÐDBC =75 °．∴∠BCD=∠DBC，∴ BD =CD ； ·································· 4 分（2）由（1）可得，∠BDC=30°，连接 OB、OC，则∠BOC=60°， ················· 6 分∴劣弧 ⌒ 的长=6p´3180=p．······························································ 8 分21．（1）（填表正确）； · ·············································································· 4 分 （2）（描点、连线正确）； · ····································································· 7 分 （3）﹣1