1/2+3/4+7/8+15/16+31/32+63/64+127/128+255/256+511/512
=9-(1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512)等比数列
=9-(1-1/512)
=8又1/512
1/2+3/4+7/8+15/16+31/32+63/64+127/128+255/256+511/512
=9-(1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512)等比数列
=9-(1-1/512)
=8又1/512