D = $2^10$ - $2^9$ + .... + $2^2$ - 2
2D = $2^11$ - $2^10$ + .... + $2^3$ - $2^2$
2D + D = ( $2^11$ - $2^10$ + .... + $2^3$ - $2^2$ ) + ( $2^10$ - $2^9$ + .... + $2^2$ - 2 )
3D = ( $2^11$ - 2 ) + ( - $2^10$ + $2^10$ ) + ... + ( - $2^2$ + $2^2$ )
3D = $2^11$ - 2
D = $\frac{2^11 - 2}{3}$
Vậy D = $\frac{2^11 - 2}{3}$