3.已知 E(X)=-2 ((X)^2)=5, 求 Var(1-3X).

3.已知 (x)=(x)^2-2x+3 , (x)=3(x)^2-x+1, 求下列-|||-(1) (x)+2g(x);-|||-(2) (x)-g(x);-|

3.已知 (2x)=x(e)^x, 则 (int )_(-1)^1|f(x)|dx= __

1． 设随机变量 X 满足 E (X ) = Var(X ) = λ ，已知 E [(X − 1) (X − 2)] = 1，试求λ ．1． 设随机变量 X 满

3.已知方程组 ) (x)_(1)+(x)_(2)+2(x)_(3)=a 3(x)_(1)-(x)_(2)-6(x)_(3)=a+2 (x)_(1)+4(x

lim _(xarrow 0)dfrac (sqrt {1+5x)-sqrt (1-3x)}({x)^2+2x}= . __

(9)lim _(xarrow 0)dfrac (sqrt {1+5x)-sqrt (1-3x)}({x)^2+2x} .

=(e)^2x-|||-2. =(e)^-(x^2)-|||-3. =dfrac ({e)^x}(1+x)-|||-4. =dfrac (sqrt {(x+1)

已知E(X)=3，D(X)=5，则E(X+2)2=______．已知E(X)=3，D(X)=5，则E(X+2)2=______．

1.计算:(3x+y+2)(3x-y-2).2.已知(3x+y+2)(3x-y-2).求（a+b-c）²。3.设x>0,且(3x+y+2)(3x-y-2).求(

3.求解线性方程组 ) (x)_(1)+2(x)_(2)-(x)_(3)+2(x)_(4)=1 2(x)_(1)+4(x)_(2)+(x)_(3)+(x)_(