\[y = - \frac{1}{4}x^{2};\ \ \ x \in \lbrack - 2;8\rbrack\]
\[y( - 2) = - \frac{1}{4} \cdot 4 = - 1;\]
\[y(0) = 0;\]
\[y(8) = - \frac{1}{4} \cdot 64 = - 16\]
\[E(y) = \lbrack - 16;0\rbrack.\]