\[4;\ - 6;\ldots\]
\[a_{1} = 4;\ \ a_{2} = - 6;\]
\[d = a_{2} - a_{1} = - 6 - 4 = - 10.\]
\[S_{8} = \frac{2a_{1} + 7d}{2} \cdot 8 =\]
\[= 4 \cdot (8 - 70) = 4 \cdot ( - 62) =\]
\[= - 248.\]