
The Equation y=mx+c is no longer needed..
Instead we use
(y - y1 )=m ( x - x1 )
m is the slope(gradient)
If it is not given
use
m=y2 - y1/x2 - x1
y - 3 = 5(x - 4)
y - 3 = 5x -20
Therefore y = 5x - 17
Simple?
Next up :
Parabola
If your focal point is in the y-axis
x^2=4py
If it is in the x-axis
y^2=4px
Engineering maths is soooo fun.......NOT!!!