у = kx + b

А ( - 2 ; - 1 ) и В ( 1 ; 4 )

[tex]\displaystyle\bf\\\left \{ {{ - 2k + b = - 1 \: \: | \times ( - 1)} \atop {k + b = 4 }} \right. \\ \displaystyle\bf\\ + \left \{ {{2k - b = 1} \atop {k + b = 4 }} \right. \\ \\ 2k + k = 1 + 4 \\ 3k = 5 \\ k = \frac{5}{3} \\ k = 1 \frac{2}{3} \\ \\ 1 \frac{2}{3} +b = 4 \\ b = 4 - 1 \frac{2}{3} \\ b = 3 \frac{3}{3} - 1 \frac{2}{3} \\ b = 2 \frac{1}{3} [/tex]

Ответ: у = 1 2/3 х + 2 1/3