A (2; −1)

B (−1; 3,5)

[tex]y = kx + b[/tex]

[tex]k:[/tex]

[tex]\left \{ {{-1=2k+b,} \atop {3,5=-k+b;}} \right.\\\left \{ {{-1=2k+b,} \atop {-3,5=k-b;}} \right.\\-4,5=3k\\k = \frac{-4,5}{3} \\k = -1,5[/tex]

[tex]b:[/tex]

[tex]-1=2*(-1,5)+b\\b = -1 + 3\\b = 2[/tex]

Ответ: [tex]y = -1,5x + 2.[/tex]