=1/2+1/8+1/32+1/128=64/128+16/128+4/128+1/128=(64+16+4+1)/128=85/128
1-1/2+1/4-1/8+1/16-1/32+1/64-1/128=1/2+1/8+1/32+1/128=85/128
=1/2+1/8+1/32+1/128=64/128+16/128+4/128+1/128=85/128
