1/1x2x3+1/2x3x4+1/3x4x5+.1/98x99x100= =1/2[1/1*2-1/2*3]+1/2[1/2*3-1/3*4]+1/2[1/3*4-1/4*5]+...+1/2[1/98*99-1/99*100] =1/2[1/1*2-1/2*3+1/2*3-1/3*4+1/3*4-1/4*5+...+1/98*99-1/99*100] =1/2[1/2-1/99*100] =1/2*4949/9900 =4949/19800
1/1x2x3+1/2x3x4.1/98x99x100拜托了各位
1个回答
相关问题
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1x1+0x1+2x2+1x2+3x3+2x3+4x4+3x4……99x99+98x99+100x100+99x100
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1X1+2X2+3X3+4X4+5X5.+98X98+99X99+100X100=?
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3x（1x2+2x3+3x4+……+99x100）= （A）97x98x99 （B）98x99x100 （C)99x 1
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100X100—99X99+98X98+...+2X2—1X1
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1/x(x+1)(x+2)+1/(x+1)(x+2)(x+3).+1/(x+98)(x+99)(x+100)=?
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100X100-99X99-98X98-97X97+…+2X2-1X1=?
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计算100X100-99X99+98X98-97X97+...+2X2-1X1=
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1/2 + 1/2 x 1/3 + 1/3 + 1/3 x 1/4.+ 1/98 +1/98 x 1/99
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1/2X3X4X5+1/3X4X5X6+1/4X5X6X7.1/97X98X99X100=?
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[1/1x2]+[1/2x3]+[1/3x4]+[1/4x5]+…+[1/99x100]．