原式=1+1-1/2+1-1/4+1-1/8+1-1/16+1-1/32+1-1/64+1-1/128
=8-(1/2+1/4+1/8+1/16+1/32+1/64+1/128),令A=1/2+1/4+1/8+1/16+1/32+1/64+1/128
则2A=1+1/2+1/4+1/8+1/16+1/32+1/64,2A-A=A=127/128
所以原式=8-127/128=7又1/128
原式=1+1-1/2+1-1/4+1-1/8+1-1/16+1-1/32+1-1/64+1-1/128
=8-(1/2+1/4+1/8+1/16+1/32+1/64+1/128),令A=1/2+1/4+1/8+1/16+1/32+1/64+1/128
则2A=1+1/2+1/4+1/8+1/16+1/32+1/64,2A-A=A=127/128
所以原式=8-127/128=7又1/128