令s=1/2+1/4+1/8+1/16+········+1/256
s/2=1/4+1/8+1/16+········+1/256+1/512
s-s/2=1/2-1/512
s/2=255/512
s=255/256
即1/2+1/4+1/8+1/16+········+1/256=255/256
令s=1/2+1/4+1/8+1/16+········+1/256
s/2=1/4+1/8+1/16+········+1/256+1/512
s-s/2=1/2-1/512
s/2=255/512
s=255/256
即1/2+1/4+1/8+1/16+········+1/256=255/256