自带电源usb集线器:1/(1*2)+1/(2*3)+1/(3*4)+........+1/(9*10) 用数学方法怎样解决?
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1 1 1 1
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1x2 + 2x3 + 3x4 + ........ + 9x10 用数学方法怎样解决?
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1x2 + 2x3 + 3x4 + ........ + 9x10 用数学方法怎样解决?
1/(1*2)+1/(2*3)+1/(3*4)+........+1/(9*10)
=(1/1-1/2)+(1/2-1/3)+……+(1/9-1/10)
=1-1/2+1/2-1/3+……+1/9-1/10
=1-1/10
=9/10