等于(1-1/2)+(1-1/4)+(1-1/8)+(1-1/16)+(1-1/32)+(1-1/64)+(1-1/128)
=7-(1/2+1/4+1/8+1/16+1/32+1/64+1/128)
=7-127/128
=6又1/128
=1-1/2+1-1/4+1-1/8+1-1/16+1-1/32+1-1/64+1-1/128
=7-(1/2+1/4+1/8+1/16+1/32+1/64+1/128)
=7-(1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/128)-1/128
=7+(1/2+1/4+1/8+1/16+1/32+1/64+1/64)-1/128)
=7+1-1/128
=7+127/128