计算(1+1/1x3)(1+1/2x4)(1+1/3x5)(1+/4x6)……(1+/11×13)
计算(1+1/1x3)(1+1/2x4)(1+1/3x5)(1+/4x6)……(1+/11×13)
x8+x7+x6+x5+x4+x3+x2+x+1因式分解
1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101
1/1X2+1/2X3+1/3X4+1/4X5+1/5X6……1/2007X2008
已知一组数据X1,X2,X3,X4,X5,X6的平均数是2,方差是1/2(急用)
求解一个方程急 X(1次方)+X2+X3=5 X2+X3+X4=1 X3+X4+X5=-5 X4+X5+X1=-3 X5
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)==?
计算:1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+1/9x10.
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)?