求通项公式0.3,0.33,0.333,0.3333,.

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求通项公式0.3,0.33,0.333,0.3333,.求通项公式0.3,0.33,0.333,0.3333,.求通项公式0.3,0.33,0.333,0.3333,.1/3(1-0.1^n)n属于n

求通项公式0.3,0.33,0.333,0.3333,.
求通项公式0.3,0.33,0.333,0.3333,.

求通项公式0.3,0.33,0.333,0.3333,.
1/3(1-0.1^n)n属于n星

1/3(1-0.1^n)n属于n星

(10^(-n)-1)/3
n=1,2,3……

看错~~

用后一项减前一项
a2-a1=0.03
a3-a2=0.003
a4-a3=0.0003
......
a(n)-a(n-1)=3*10^(-n)
然后用上面等式的左边加左边,右边加右边。
应该会了吧!