某学生依次进行三门课程的考试,第一门课程考试及格的概率为dfrac (4)(5),以后各门课程考试及格的概率均根据前一门课程考试及格或不及格分别为dfrac (4)(5)和dfrac (4)(5).则该学生第三门课程及格的概率为(). A dfrac (4)(5);B dfrac (4)(5);C dfrac (4)(5);D dfrac (4)(5).

[题目]-|||-(5) lim _(narrow infty )dfrac ({(-2))^n+(3)^n}({(-2))^n+1+(3)^n+1} ;

11.设随机变量X与Y相互独立且同在区间 (0,theta )(theta gt 0) 上服从均匀分布,则-|||-[ min X,Y ] = () 。-|||-A. dfrac (theta )(2) B.θ C. dfrac (theta )(3) D. dfrac (theta )(4)

求空间一点(x_(0)，y_(0)，z_(0))到平面Ax+By+Cz+D=0的最短距离.

17.单选题(5分)箱子里有5 双不同尺码的鞋子，从中任取4 只，则只有一对鞋子的概率为（）A dfrac (5)(21);B dfrac (5)(21);C dfrac (5)(21);D dfrac (5)(21).

(5) lim _(xarrow 0)dfrac (tan x-sin x)({x)^3}

(7) lim _(xarrow +infty )(sqrt ({x)^2+x}-sqrt ({x)^2-x}) ;

1.利用 lim _(narrow infty )((1+dfrac {1)(n))}^n=e 求下列极限:-|||-(1) lim _(narrow infty )((1-dfrac {1)(n))}^n;-|||-(2) lim _(narrow infty )((1+dfrac {1)(n))}^n+1;-|||-(3) lim _(narrow infty )((1+dfrac {1)(n+1))}^n;

在一周内甲,乙,丙三台机床需维修的概率分别是0.9 0.8和0.85,则一周内至多只有一台机床需要维修的概率为().A. 0.002;B. 0.388;C. 0.003;D. 0.0

(9) =dfrac (sqrt {1+x)-sqrt (1-x)}(sqrt {1+x)+sqrt (1-x)} ;

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