Prove that the equation of the line through the distinct poi
     Prove that the equation of the line through the distinct points (a_1, b_1) and (a_2, b_2) can also be written as |x  a_1  a_2  y  b_1  b_2  1  1  1| = 0. 
  
  Solution
Solving the given equation as:
x (b1*1 - b2*1) - y (a1*1 - a2*1) + 1 (a1*b2 - a2b1) = 0
x (b1 - b2) -y (a1 - a2 ) + a1b2 - a2b1 = 0 ------------ (1)
Now let us find the equation of the line passing through points (a1, b1) and (a2, b2).
I am using the point slope equation as:
y - b1 = m (x - a1)
y - b1 = (b1-b2)/(a1-a2) * (x - a1)
Multiply both the sides by (a1 - b1), we get:
(y-b1)(a1-a2) = (x-a1)(b1-b2)
y (a1 - a2) - b1a1 + a2b1 = x (b1 - b2) - a1b1 + a1b2
x (b1 - b2) - y (a1 - a2) + a1b2 - a2b1 = 0 -------------- (2)
Comparing equation (1) and (2), we can see that both are equal.
Hence Proved.

