
If three points (x_{1}, y_{1}), (x_{2}, y_{2}), (x_{3}, y_{3}) lie on a straight line, the area of the triangle formed by them is zero. i.e1/2(x_{1}y_{2}x_{2}y_{1}+x_{2}y_{3}x_{3}y_{2}+x_{3}y_{1}x_{1}y_{3}) = 0
Example: Show that the points (a,b+c),(b,c+a) and (c, a+b) are collinear. Directions: Solve the following problems. 