\[f(x) = \frac{1}{2}x^{2} - 3x\]
\[f(2) = \frac{1}{2} \cdot 4 - 3 \cdot 2 = 2 - 6 = - 4.\]
\[f( - 3) = \frac{1}{2} \cdot 9 + 3 \cdot 3 = 4,5 + 9 = 13,5.\]