3.设 approx U[ -1.5] , 则X的方差 (x)= ().()-|||-(A)3 (B)2 (C) -3 (D) dfrac (4)(3)

3.设 approx N(0,(4)^2), approx N(1,(3)^2), 且 (rho )_(x)=-dfrac (1)(2), 令 =dfrac (

4.10 设随机变量X 1,X2,X3相互独立,且 _(1)approx B(4,dfrac (1)(2)) _(2)approx B(6,dfrac (1)(

3.设 =xarcsin dfrac (x)(2)+sqrt (4-{x)^2} 则 dy= __ 。

、设随机变量 approx P(lambda ), 已知 (X=1)=P(X=2), 则 P(X=4)=-|||-A) dfrac (1)(3)(e)^2 (B

3.设 (x)=dfrac (1)(1+2x+4{x)^2} 则 ^(100)(0)= __

(B) =-dfrac (x)(2)+dfrac (3)(2)-|||-(C) =dfrac (x)(2)+dfrac (3)(2) (D) =-dfrac (

lim _(xarrow 4)dfrac (sqrt {1+2x)-3}(x-4)= (-|||-A dfrac (2)(3) .-|||-B 2-|||-C

2.设D |x|+|y|leqslant 1, 则 iint (|x|+y)dxdy= () .-|||-(A)0 (B) dfrac (1)(3) (C) d

3.求下列极限:-|||-(1) lim _(xarrow 2)dfrac ({x)^2-3x-4}({x)^2-4} =-|||-(3) lim _(xarr

3.求下列极限:-|||-(1) lim _(xarrow 2)dfrac ({x)^2-3x-4}({x)^2-4} :-|||-(3) lim _(xarr