1x2x3+2x3x4+3x4x5+...+7x8x9=,
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1x2x3+2x3x4+3x4x5+...+7x8x9=,1x2x3+2x3x4+3x4x5+...+7x8x9=,1x2x3+2x3x4+3x4x5+...+7x8x9=,因为1x2x3=(1x2x
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2x3+2x3x4+3x4x5+...+7x8x9=,
因为1x2x3=(1x2x3×4-0x1x2×3)/4
2x3x4=(2x3x4×5-1x2x3×4)/4
.
7x8x9=(7x8x9×10-6x7x8x9)/4
所以 1x2x3+2x3x4+3x4x5+…+7x8x9
=(1x2x3×4-0x1x2×3)/4+(2x3x4×5-1x2x3×4)/4+...(7x8x9×10-6x7x8x9)/4
=(7x8x9×10)/4
=1260
1x2x3+2x3x4+3x4x5+…+8x9x10
1x2x3+2x3x4+3x4x5+.+10x11x12
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2X3+2x3X4+3x4X5+…+7X8X9=?
1x2x3 2x3x4 3x4x5 .10x11x12,怎么算
求和：1X2X3+2X3X4+3X4X5+...+98X99X100
1x2=1|3(1x2x3-0x1x2) 2x3=1|3(2x3x4-1x2x3) 3x4=1|3(3x4x5-2x3x4)由此推断1x2x3+2x3x4+3x4x5.7x8x9=?
1x2=1/3x(1x2x3-0x1x2)2x3=1/3x(2x3x4-1x2x3)3x4=1/3x(3x4x5-2x3x4)求1x2x3+2x3x4+3x4x5+...+7x8x9=?
1/1x2x3+1/2x3x4+1/3x4x5+.+1/n(n+1)(n+2)
2/1x2x3+2/2x3x4+2/3x4x5+2/4x5x6+...+2/98x99x100=
1/1x2x3+1/2x3x4+1/3x4x5+.+1/8x9x10 求简算
请1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6=
1/1x2x3+1/2x3x4+1/3x4x5+------+1/98x99x100=
1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(20x21x22)=?
1/1x2x3+1/2x3x4+1/3x4x5+.+1/9x10x11=
1/1x2x3+1/2x3x4+1/3x4x5+.1/98x99x100=要有中间过程
1/1x2x3+1/2x3x4+1/3x4x5+.+1/11x12x13=
1x2x3+2x3x4+3x4x5+4x5x6+...+n(n+1)(n+2)=