$D$ = $-1$ - $2^{2}$ - $2^{3}$ - ..... - $2^{2018}$
⇔$2D$= $-2$ - $2^{3}$ - $2^{4}$ - ..... - $2^{2019}$
⇔$2D-D$ = ($-2$ - $2^{3}$ - $2^{4}$ - ..... - $2^{2019}$) -
($-1$ - $2^{2}$ - $2^{3}$ - ..... - $2^{2018}$)
⇔$D$=$-2+1$ + $2^{2}$ - $2^{2019}$
⇔$D$ =$-1 + 4$ - $2^{2019}$
⇔$D$ = $3$ - $2^{2019}$
Vậy $D$ = $3$ - $2^{2019}$