19、单选 lim _-|||-A 1-|||-B) dfrac (4)(9)-|||-C dfrac (2)(3)-|||-D dfrac (9)(4)
函数=dfrac (1)({3)^x-9}的定义域是( )=dfrac (1)({3)^x-9}=dfrac (1)({3)^x-9}=dfrac (1)(
(4)已知 =xln x, 则 y(10) 等于 ()-|||-(A) -dfrac (1)({x)^9} (B) dfrac (1)({x)^9} (C) d
(B) dfrac (9)(4pi {varepsilon )_(0)a}-|||-(C) -dfrac (9)(8pi {varepsilon )_(0)a}
dfrac (7)(2) D. dfrac (9)(2)
设随机变量X与Y的联合分布律为X/Y 1 2 3-|||-1 1/9 2/9 2/9-|||-2 0 dfrac (1)(9) dfrac (2)(9)-|||
E: dfrac (9)(12{varepsilon )_(0)} .:dfrac (9)(24{c)_(0)}
不定积分int dfrac (dx)(4{x)^2-9}=-|||-__.int dfrac (dx)(4{x)^2-9}=-|||-__int dfrac (
dfrac (9)(25)times 101-9div 25dfrac (9)(25)times 101-9div 25
计算下面两个图形的面积。-|||-dfrac (4)(9)dm-|||-3/4dm-|||-.dfrac (11)(18)m-|||-.dfrac (2)(3)