Vẽ đồ thị hàm số y=3x^2

\begin{array}{|c|c|c|c|c|c|}\hline \text{x}&\text{-2}&\text{-1}&\text{0}&\text{1}&\text{2}\\\hline \text{y}&\text{12}&\text{3}&\text{0}&\text{3}&\text{12}\\\hline \end{array}