8.
[tex]\begin{gathered} \text{let:} \\ (x1,y1)=(-1,4) \\ (x2,y2)=(2,-2) \\ \text{the slope is:} \\ m=\frac{y2-y1}{x2-x1}=\frac{-2-4}{2-(-1)}=\frac{-6}{3}=-2 \end{gathered}[/tex]Using the point-slope equation:
[tex]\begin{gathered} y-y1=m(x-x1) \\ y-4=-2(x-(-1)) \\ y=-2x+2 \end{gathered}[/tex]9.
[tex]\begin{gathered} \text{let:} \\ (x1,y1)=(2,1) \\ m=2 \end{gathered}[/tex]Using the slope-point equation:
[tex]\begin{gathered} y-y1=m(x-x1) \\ y-1=2(x-2) \\ y=2x-3 \end{gathered}[/tex]