1x2÷1+2x3÷1+3x4÷1+4x5÷1+5x6÷1.+n(n+1)÷1
(x1,x2,x3,x4,x5,x6)来自正态总体N(0,1),Y=(x1+x2+x3)^2+(x4)^2+(x5)^2
1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101
设X1,X2,X3,X4,X5,X6是来自总体N(0,1)的样本,为什么X1+X2+X3~N(0,3)?
一道简便计算数学题1X2+2X3+3X4+4X5...+n(n+1)一1X2+2X3+3X4+4X5...+2013X2
)设X服从N(0,1),(X1,X2,X3,X4,X5,X6)为来自总体X的简单随机样本,Y=(X1+X2+X3+)^2
x8+x7+x6+x5+x4+x3+x2+x+1因式分解
1/1X2+1/2X3+1/3X4+1/4X5+1/5X6……1/2007X2008
1x2/1+2x3/1+3x4/1+4x5/1+5x6/1+6x7/1
1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+......1/2008x2009
1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7
(2X2)/1X3+(4X4)/(3X5)+(6X6)/(5X7)+...+(20X20)/(19X21)==?
84÷63X3 1X5.3+2.1X6.2-2.1X1.5