1/2X3X4X5+1/3X4X5X6+1/4X5X6X7.1/97X98X99X100=?
=1/3[1/2*3*4-1/3*4*5]+1/3[1/3*4*5-1/4*5*6]+1/3[1/4*5*6-1/5*6*7]+...+1/3[1/97*98*99-1/98*99*100]
=1/3[1/2*3*4-1/98*99*100]
=1/3*40424/98*99*100
=5053/3*49*99*25
1/2X3X4X5+1/3X4X5X6+1/4X5X6X7.1/97X98X99X100=?
1个回答
相关问题
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1X1+2X2+3X3+4X4+5X5.+98X98+99X99+100X100=?
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1 1 1 1 1 ——＋——＋——＋——＋```````` —— 2X3 3X4 4X5 5X6 99X100
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1/1x2x3x4+1/2x3x4x5+1/3x4x5x6+1/4x5x6x7+1/5x6x7x8+1/6x7x8x9+
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3x（1x2+2x3+3x4+……+99x100）= （A）97x98x99 （B）98x99x100 （C)99x 1
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1/1X2+1/3X4+1/5X6+……+1/99X100=?
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1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101
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3x+7=4x+5,4x-6=-3+5x,2x+1-x=3-3x,3x-1=x,3x-2=5x-6,4x+5=3x+3-
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1/2X1/3+1/3X1/4+1/4X1/5+1/5X1/6+.+1/99X1/100=?
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1x1+0x1+2x2+1x2+3x3+2x3+4x4+3x4……99x99+98x99+100x100+99x100