+(a)_(n)(x)^n. 若点 _(i)(i,(a)_(i))(i=0,1,2) 的位置如图-|||-所示,则 a= __ .-|||-y-|||-4 A2-|||-3-|||-1.A0 1-|||-1-|||-0 1 2 x

若 Y=X_(1)+X_(2)，X_(i) sim N(0,1)，i=1,2，则（）A. $E(Y)=0$；B. $D(Y)=2$；C. $Y \sim N(0

,n)独立同分布，方差为_(i)(i=1,2,... ,n) , _(i)(i=1,2,... ,n) ，则( ) ( A )_(i)(i=1,2,.

若_(i)sim N(0,1), =1,2,(X)_(1),(X)_(2)独立，则_(i)sim N(0,1), =1,2,(X)_(1),(X)_(2)()A

设X_i sim N(0, 4), i=1, 2, 3, 且相互独立, 则 ()成立。A. $\frac{X_1}{4} \sim N(0,1)$B. $\fr

3.设X_(1),...,X_(10)为来自标准正态总体Xsim N(0,1)，Y_(1)=7sum_(i=1)^3X_(i)^2,Y_(2)=3sum_(i=

1-|||-1 a1 0 ····0-|||-计算 n+1 阶行列式 _(n+1)= 1 0 a2 ... 0 _(i)neq 0(i=1,2,... ,n).

设复数_(1)=(x)_(1)+i(y)_(1), _(2)=(x)_(2)+i(y)_(2)，且_(1)=(x)_(1)+i(y)_(1), _(2)=(x)

(B) dfrac (1)(n+1)sum _(i=1)^n(({X)_(i)-overline (X))}^2 .-|||-(C) dfrac (1)(n)s

令 Y = (1)/(n) sum_(i=1)^n X_i，则A. $\Cov(X_1, Y)= \frac{\sigma^2}{n}$.B. $Cov(X_1

) 相互独立,具有同一分布, ((X)_(i))=0, ((X)_(i))=(sigma )^2,i=1,2,... ,,-|||-则当n很大时, sum _(