Hello
an equation for the line in point-slope form and general form is :
y = ax+b a : slope ; the Passing through (x' ; y')
y' = ax'+b
y-y' =a(x-x') and : x' =8 y' = -4
calculate a :
let : y = ax+b .....(D)
....(D') y = (1/5)x+4
.(D) perpendicular to(D') : slope (D) × slope (D') = -1
slope (D') = 1/5
slop(D)×(1/5) = -1
slope (D) = -5
equation for the line : y-y' =a(x-x')
y+4 =(-5) (x-8)