10片药片中有5片是安慰剂.(1) 从中任意抽取5片，求其中至少有2片是安慰剂的概率.

【题目】-|||-将xOy坐标面上的双曲线 (x)^2-9(y)^2=36 分别绕x轴及y轴旋转一周,-|||-求所生成的旋转曲面的方程,

已知事件A,B满足 (AB)=P(overline (A)overline (B)), 则下式错误-|||-的是 ()-|||-square A. (AB)=P(overline (A)overline (B))Longrightarrow A, B对立-|||-square B. (AB)=P(overline (A)overline (B))Longrightarrow P(AB)=0-|||-square C. (AB)=P(overline (A)B)Longrightarrow P(A)+P(overline (B))=1-|||-square D. (AB)=P(overline (A)overline (B))Longrightarrow AB=overline (A)overline (B)

21.已知男子有5%是色盲患者，女子有0.25%是色盲患者。今从男女人数相等的人群随机地挑选一人，恰好是色盲患者，问此人是男性的概率是多少？

(1)一个三角形最多有几个直角？为什么？

(4)设 =(x)^2-2xy+3(y)^2, 则 zxy= __ ;

lim _(xarrow 0)dfrac (sin (x{y)^2)}({y)^2}=______.

1.求下列不定积分:-|||-(1) int dfrac ({x)^3}(x-1)dx;-|||-(2) int dfrac (x-2)({x)^2-7x+12}dx;-|||-(3) int dfrac (dx)(1+{x)^3};-|||-(4) int dfrac (dx)(1+{x)^4};-|||-(5) int dfrac (dx)((x-1){({x)^2+1)}^2} ;-|||-(6) int dfrac (x-2)({(2{x)^2+2x+1)}^2}dx

9.设x_(1)=sqrt(2),x_(n+1)=sqrt(2+x_(n))(n=1,2,...),试证数列(x_{n)}极限存在,并求此极限.

5.将下列曲线的一般方程化为参数方程:-|||-(1) ) (x)^2+(y)^2+(z)^2=9 y=x; .

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