\[\boxed{\text{318\ (318).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = - 3x + 1,5\ \ \ \ \]
\[\textbf{а)}\ если\ x = - 1,5:\]
\[y = - 3 \cdot ( - 1,5) + 1,5 =\]
\[= 4,5 + 1,5 = 6;\]
\[если\ x = 2,5:\]
\[y = - 3 \cdot (2,5) + 1,5 =\]
\[= - 7,5 + 1,5 = - 6;\]
\[если\ x = 4:\]
\[y = - 3 \cdot 4 + 1,5 = - 12 + 1,05 =\]
\[= - 10,5.\]
\[\textbf{б)}\ Выразим\ \text{x\ }через\ y:\]
\[- 3x = y - 1,5\]
\[3x = 1,5 - y\]
\[x = \frac{1,5 - y}{3}.\]
\[если\ \ y = - 4,5:\]
\[x = \frac{1,5 + 4,5}{3} = \frac{6}{3} = 2;\]
\[если\ \ y = 0:\]
\[x = \frac{1,5 - 0}{3} = \frac{1,5}{3} = 0,5;\]
\[если\ \ y = 1,5:\]
\[x = \frac{1,5 - 1,5}{3} = \frac{0}{3} = 0.\]