(x-1) /1 -( x+1) /1 - (x2+1 )/2 - (x4+1)/4 -(x8+1)/8
=(x^2-1)/1- (x2+1 )/2 - (x4+1)/4 -(x8+1)/8
=(x^4-1)/4- (x4+1)/4 -(x8+1)/8
=(x8-1)/8-(x8+1)/8
=(x^16-1)/16