Answer :
[tex]x_1=1 \\ y_1=-2 \\ \\ x_2=2 \\ y_2=-6 \\ \\
m=\frac{y_2-y_1}{x_2-x_1}=\frac{-6-(-2)}{2-1}=\frac{-6+2}{1}=\frac{-4}{1}=-4 \\ \\
y=-4x+b \\
x=1, y=-2 \\
-2=-4 \times 1+b \\
-2=-4+b \\
-2+4=b \\
b=2 \\ \\
\boxed{y=-4x+2}[/tex]