已知$x_{1}[k]=\{-1,1,0,2,1,0,-1\}$，$x_{2}[k]=\{1,2,3,-1,-1,-1,-1\}$，画出下列离散序列的波形。
(1) $y_{1}[k]=x_{1}[k]+x_{2}[k]$;
(2) $y_{2}[k]=x_{1}[k]x_{2}[k]$;
(3) $y_{3}[k]=x_{1}[2k]+x_{2}[3k]$;
(4) $y_{4}[k]=x_{1}[k+1]+x_{2}[-k]$;
(5) $y_{5}[k]=\sum_{n=-\infty}^{k}x_{1}[n]$;
(6) $y_{6}[k]=x_{2}[k]-x_{2}[k-1]$。
37.已知x_{n)},y_{n)}满足：x_(1)=y_(1)=(1)/(2),x_(n+1)=sin x_(n),y_(n+1)=y_(n)^2(n=1,2
已知随机变量X_(1), X_(2), X_(3)的协方差COV(X_(1), X_(3)) = 2, COV(X_(2), X_(3)) = 1。则COV(X
1.17 二次型 f(x_(1),x_(2))=x_(1)^2-2x_(2)^2+4x_(1)x_(2)bigcirc y_(1)^2-2y_(2)^2bigc
用plotyy函数绘制函数 y_(1)=sin x_(1),x_(1)in[0,2pi],y_(2)=x_(2)+5,x_(2)in[1,10]，其表达式为（）
X_(4))为来自总体X的简单随机样本，则k=（ ）时，Y=k[(X_(1)-X_(2))^2+(X_(3)-X_(4))^2]sim X^2(2).A. 16
1 设总体Xsim N(0,1)，X_(1),X_(2),...,X_(n)为X的样本，则((X_(1)-X_(2))/(X_(3)+X_{4)})^2服从__
(3)设X_(1)sim N(1,2),X_(2)sim N(0,3),X_(3)sim N(2,1),且X_(1),X_(2),X_(3)相互独立，则P0le
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