Use the given conditions to write an equation for the line in point-slope form and in slope-interception for. passing through (8,-4) and perpendicular to the line whose equations is y=1/5x+4

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)