Question

Show that the following points are collinear:

A(5, 1), B(1, –1) and C(11, 4)

Answer 1

`"Let" A(x_1=5,y_1=1), B(x_2=1,y_2=-1) and C(x_3=11,y_3=4)`be the given points. 

Now   `x_1 (y_2-y_3)+x_2(y_3-y_1)+x_3(y_1-y_2)`

=5(-1-4)+1(4-1)+11(1+1)

=-25+3+22

=0

Hence, the given points are collinear.