Let:
[tex]y=-x-8[/tex]From that equation:
[tex]m1=-1[/tex]If two lines are perpendicular, then:
[tex]\begin{gathered} m1\times m2=-1 \\ m2=1 \end{gathered}[/tex]Given an arbitraty point:
[tex](x1,y1)=(1,2)[/tex]Using the point slope equation:
[tex]\begin{gathered} y-y1=m(x-x1) \\ y-2=1(x-1) \\ y-2=x-1 \\ y=x+1 \end{gathered}[/tex]