[tex]y = kx + b \\ (3; \: - 4) \: \: \: \: \: ( - 1; \: 8) \\ \displaystyle\bf\\\left \{ {{3k + b = - 4} \atop { - k + b = 8 \: \: | \times( - 1)}} \right. \\ \displaystyle\bf\\ + \left \{ {{3k + b = - 4} \atop {k - b = - 8 }} \right. \\ \\ 3k + k = - 8 - 4 \\ 4k = - 12 \\ k = - 12 \div 4 \\ k = - 3 \\ \\ - ( - 3) + b = 8 \\ b = 8 - 3 \\ b = 5 \\ \\ otvet \: \: \: \: y = - 3x + 5[/tex]