箱子里装有10个大小相同的编号为1、2、3的小球,其中1号小球有2个,2号小球有m,3号小球有n个,且m<n.从箱子里一次摸出两个球号码是2号和3号各一个的概率是
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(1)求m,n的值;
(2)从箱子里一次任意摸出两个球,设得到小球的编号数之和为ξ,求随机变量ξ的分布列和数学期望.
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已知:函数
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.
(1)求函数f(x)的最小正周期和值域;
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,
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.求
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的值.
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如图,设矩形ABCD(AB>AD)的周长是20,把三角形ABC沿AC折起来,AB折过去后,交DC于点F,设AB=x,则三角形ADF的面积最大时的x的值为
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已知对任意平面向量
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后得到点的轨迹是曲线x
2-y
2=2,则原来曲线C的方程是
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已知向量
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,
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中,2
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-
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=(
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),
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=(1,
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),
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=3,|
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|=4,则
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与
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的夹角为
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将号码分别为1、2、3、…、9的九个小球放入一个袋中,这些小球仅号码不同,其余完全相同.甲从袋中摸出一个球,其号码为a,放回后,乙从此袋中再摸出一个球,其号码为b.则使不等式a-b>0成立的事件发生的概率等于
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