原式=1-1/2+1-1/+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
底数全部换成128。1/2+3/4+7/8+15/16+31/32+63/64+127/128=64/128+96/128+112/128+120/128+124/128+126/128+127/128=619/128