1x2+2x3+3x4+...+n(n+1)=?1x2x3+2x3x4+3x4x5+...+n(n+1)(n+2)=?
1x2x3+2x3x4+3x4x5+4x5x6+...+n(n+1)(n+2)=
1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(nx(n+1)x(n+2)=?
求和1x2x3+2x3x4+...+n(n+1)(n+2)
1x2=1/3(1x2x3=0x1x2 ) 2x3=1/3(2x3x4-1x2x3) 3x4=1/3(3x4x5- 2x
1x2=1|3(1x2x3-0x1x2) 2x3=1|3(2x3x4-1x2x3) 3x4=1|3(3x4x5-2x3x
1x2=三分之一{1x2x3-0x1x2};2x3-三分之一{2x3x4-1x2x3}:3x4-三分之一{3x4x5-2
1x2=(1/3)(1x2x3-0x1x2) 3x4=(1/3)(3x4x5-2x3x4) 问1x2x3+2x3x4+.
数学题目,求速度1x2十2x3+…+100x101=1x2+2x3+…+n(n十1) 1x2x3+2+3x4+…+n(n
1x2X3+2x3X4+3x4X5+…+7X8X9=?
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2+2x3+3x4+...+n(n+1)=?
3.1x2x3+2+3x4+…+n(n+1)(n+2)