у = kx + b

М (0; -12) i K (-3; 0)

[tex]\displaystyle\bf\\\left \{ {{b = - 12} \atop { - 3k + b = 0 }} \right. \\ \\ - 3k - 12 = 0 \\ 3k = - 12 \\ k = - 12 \div 3 \\ k = - 4[/tex]

Ответ: k = - 4 ; b = - 12