\[\boxed{\text{1042\ (1042).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = 6 - kx;\ \ \ \ A\ (4; - 2)\]
\[- 2 = 6 - 4k\]
\[- 4k = - 8\]
\[k = 2\]
\[Ответ:при\ k = 2.\ \]
\[\boxed{\text{1042.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[если\ x = 2:\ \ \ \ \ \ \]
\[{\ a}^{2} - 2 \cdot 2 = a^{2} - 4 =\]
\[= (a - 2)(a + 2);\]
\[если\ x = 8:\ \]
\[\ a^{2} - 2 \cdot 8 = a^{2} - 16 =\]
\[= (a - 4)(a + 4);\]
\[если\ x = 18:\ \]
\[a^{2} - 2 \cdot 18 = a^{2} - 36 =\]
\[= (a - 6)(a + 6).\]