First, we must determine the slope:
Slope = m = (Y2 -Y1) ÷ (X2 -X1)
Slope = (-1, -3) / (2 -5)
Slope = -4 / -3 = 4 / 3 = 1.33333333...
Now, we have to fill in this equaton:
y = mx + b we know the slope "m"
y = 1.3333... x + b now we'll take a point (5, 3) and solve for "b"
b = y -mx b = 3 - 1.3333... *5
b = -3.6666666667
y = 1.3333... x -3.6666...
Source
1728.com/distance.htm