Question

Find the slope of AB, A(0,-1), B(-4,-5) then find the slope of the line perpendicular to AB

I just need a sort of formula to work out this type of problem so I can solve the rest myself.

Answer 1

If you points are (a,b) and (c,d),
slope = (d-b) / (c-a) or (b-d)/(a-c)

if the slope of some line is p/q , then the slope of its perpendicular is - q/p

e.g.
Your points ...
slope = (-5 - (-1) ) / (-4 - 0)
= (-5 + 1)/-4
=-4/-4
= 1
so the slope of its perpendicular is -1/1 = -1