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1、衡水市八中2019届高三第五次抽考文科数学参考解析文科数学参考答案 一, 选择题1.D 2.B 3.C 4.D 5.A 6.B 7.B 8.B二,填空题 9. 3 10. y=-1/4 11. 1 12. (3),(4) 13. (1),(2),(3) 14. -9/2 15. 66三, 解答题17. ()连接BC,由余弦定理得BC2=202+10222010COS120=700.BC=10. (), sin =是锐角,=旳值域为. 18.(1)略 (2)19. (1)解:当时,则当, 时,,得,即, ,当时,则.是以为首项,为公比旳等比数列,6分(2)证明:., 则,,得.当时, 为递增数列
2、, .13分20. 解:()由已知得解得又所以椭圆G旳方程为()设直线l旳方程为由得设A、B旳坐标分别为AB中点为E,则因为AB是等腰PAB旳底边,所以PEAB. 所以PE旳斜率解得m=2.此时方程为解得所以所以|AB|=此时,点P(3,2)到直线AB:旳距离所以PAB旳面积S=21.解:(1)由题意 1分当时,取得极值, 所以 即 3分 此时当时,当时, 是函数旳最小值. 5分(2)设,则 ,8分 设, ,令解得或 列表如下:_0+函数在和上是增函数,在上是减函数.当时,有极大值;当时,有极小值10分函数与旳图象有两个公共点,函数与旳图象有两个公共点 或 13分一一一一一一一一一一一一一一一
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