\[\boxed{\text{444\ (444).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[5x - y = 2;\ \ A\ (4;b):\]
\[5 \cdot 4 - y = 2\]
\[20 - 2 = y\]
\[18 = y\]
\[b = 18\]
\[Ответ:b = 18.\]
\[\boxed{\text{444.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ x_{0} = - \frac{b}{2a}\]
\[- \frac{b}{2a} = 1\]
\[b = - 2a\ \ \]
\[a = 1 \rightarrow b = - 2:\]
\[y = x^{2} - 2x.\]
\[2)\ x_{0} = - \frac{b}{2a}\]
\[- \frac{b}{2a} = - 2\ \]
\[a = - 1 \rightarrow b = - 4.\]
\[y = - x^{2} - 4x.\]