\[4;\ - 6;\ldots\]
\[a_{1} = 4;\ \ a_{2} = - 6;\]
\[d = a_{2} - a_{1} = - 6 - 4 = - 10.\]
\[S_{18} = \frac{2a_{1} + 17d}{2} \cdot 18 =\]
\[= 9 \cdot (8 - 170) = 9 \cdot ( - 162) =\]
\[= - 1458.\]