\[\boxed{\text{293\ (293).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ y = ax^{2}\]
\[точка\ (2;6):\]
\[6 = a \cdot 2^{2}\]
\[a = \frac{6}{4}\]
\[a = 1,5.\]
\[\textbf{б)}\ y = ax^{2}\]
\[точка\ (3;\ - 3)\]
\[- 3 = a \cdot 3^{2}\]
\[a = - \frac{3}{9}\]
\[a = - \frac{1}{3}.\]