Answer :
[tex]\bf (\stackrel{x_1}{4}~,~\stackrel{y_1}{-9})~\hspace{10em} \stackrel{slope}{m}\implies -6 \\\\\\ \begin{array}{|c|ll} \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-\stackrel{y_1}{(-9)}=\stackrel{m}{-6}(x-\stackrel{x_1}{4}) \\\\\\ y+9=-6x+24\implies y=-6x+15[/tex]