=1-1/2-(1/2)^2-(1/2)^3-(1/2)^4-(1/2)^5-.-(1/2)^10
等比数列
=1-(1/2)*(1-(1/2)^10)/(1-(1/2))
=(1/2)^10=1/1024
另外,如果一个一个算下去会发现
=1/2-1/4-1/8.-1/1024
=1/4-1/8-.-1/1024
=1/8-...-1/1024
...
=1/1024