1/2x3X4十1/3X4x5十1/4X5X6……十1/8X9X10等于多少最好给个详细答案谢谢
来源:学生作业帮 编辑:神马作文网作业帮 分类:数学作业 时间:2024/09/23 23:25:15
1/2x3X4十1/3X4x5十1/4X5X6……十1/8X9X10等于多少最好给个详细答案谢谢
1/2x3X4=(1/2X3-1/3X4)X1/2
1/3X4x5=(1/3X4-1/4X5)X1/2
.1/8X9X10=(1/8X9-1/9X10)X1/2
上述各式相加得:
1/2x3X4十1/3X4x5十1/4X5X6……十1/8X9X10
=(1/2X3-1/3X4+1/3X4-1/4X5+.+1/8X9-1/9X10)X1/2
=(1/2X3-1/9X10)X1/2
=(1/6-1/90)X1/2
=(15/90-1/90)X1/2
=14/90 X 1/2
=7/90 再答: 不客气
1/3X4x5=(1/3X4-1/4X5)X1/2
.1/8X9X10=(1/8X9-1/9X10)X1/2
上述各式相加得:
1/2x3X4十1/3X4x5十1/4X5X6……十1/8X9X10
=(1/2X3-1/3X4+1/3X4-1/4X5+.+1/8X9-1/9X10)X1/2
=(1/2X3-1/9X10)X1/2
=(1/6-1/90)X1/2
=(15/90-1/90)X1/2
=14/90 X 1/2
=7/90 再答: 不客气
1/2x3X4十1/3X4x5十1/4X5X6……十1/8X9X10等于多少最好给个详细答案谢谢
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1x2x3+2x3x4+3x4x5+…+8x9x10
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