[tex]\bf \begin{array}{c|c|c|cl} -2\cdot (-3)^0&-2\cdot (-3)^1&-2\cdot (-3)^2&-2\cdot (-3)^3\\&&&\\ \cline{1-4} &&&\\ -2&6&-18&54 \end{array}~\hfill \displaystyle\sum\limits_{i=0}^{3}~-2(-3)^i[/tex]
