2/1x2x3+2/2x3x4+2/3x4x5+2/4x5x6+...+2/98x99x100=
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2/1x2x3+2/2x3x4+2/3x4x5+2/4x5x6+...+2/98x99x100=
原式=(1/1*2-1/2*3)+(1/2*3-1/3*4)+……(1/98*99-1/99*100)
=1/1*2-1/99*100
=49499/99000
=1/1*2-1/99*100
=49499/99000
1/1x2x3+1/2x3x4+1/3x4x5+.1/98x99x100=
1x2x3+2x3x4+3x4x5+4x5x6+...+n(n+1)(n+2)=
1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+.+1/48x49x50=
请1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6=
1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+1/5x6x7=?这类题
1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+...+1/8x9x10 等于多少?
1x2X3+2x3X4+3x4X5+…+7X8X9=?
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2x3=6 3x4x5=60 5x6x7=210 2x3x4=24 4x5x6=120三个连续自然数(0除外)的乘积
1/2x3x4+1/3x4x5+1/4x5x6+……+1/48x49x50=
1/1x2x3+1/2x3x4+1/3x4x5
1x2x3+2x3x4+3x4x5+…+8x9x10