Tính f(0), f(1), f(-2), f(4).

* Hướng dẫn giải

 \(\begin{array}{l}f\left( 0 \right) = \dfrac{1}{2}{.0^2} = 0\\f\left( 1 \right) = \dfrac{1}{2}{.1^2} = \dfrac{1}{2}\\f\left( { - 2} \right) = \dfrac{1}{2}.{\left( { - 2} \right)^2} = 2\\f\left( 4 \right) = \dfrac{1}{2}{.4^2} = 8\end{array}\)