1-1/10-1/100-1/1000-.-1/100000000=?简便计算过程

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1-1/10-1/100-1/1000-.-1/100000000=?简便计算过程

1-1/10-1/100-1/1000-.-1/100000000=?简便计算过程
1-1/10-1/100-1/1000-.-1/100000000=?简便计算过程

1-1/10-1/100-1/1000-.-1/100000000=?简便计算过程
1-1/10-1/100-1/1000-.-1/100000000
=1-0.1-0.01-0.001-0.0001-……-0.00000001
=1-(0.1+0.01+0.001+0.0001+……+0.00000001)
=1-0.11111111
=0.88888889

1-1/10-1/100-1/1000-......-1/100000000=1-11111111/100000000=88888889/100000000

=0.8888 8889
因为
1=0.9999 9999 + 0.0000 0001,也就是拆成两部分
然后用它去分别减 1/10 1/100 1/1000-......-1/100000000
你会发现就是把0.9999 9999 各个数位上的9减1,得到0.8888 8888
最后再加上拆出来的0.0000 0001,把它加回去,就是0.8888 8889

设A=1-1/10-1/100-1/1000-......-1/100000000
10A=10-1-1/10-1/100-……-1/10000000
10A-A=(10-1-1/10-1/100-……-1/10000000)-(1-1/10-1/100-1/1000-......-1/100000000)
9A=9-1/100000000
A=1-1/900000000
A=899999999/900000000
1-1/10-1/100-1/1000-......-1/100000000=899999999/900000000

1-1/10-1/100-1/1000-......-1/100000000=1-(1/10+1/100+1/1000+......+1/100000000)=1-(1-0.1^8)/(1-0.1)=-0.9999999988888888889(八循环)