Question 136922
hi,

The slope of the line joining (3,1) and (6,3) = (3-1)/(6-3)
                                              = 2/3 -------------(1)

The slope of the line joining (6,3)and (2,9) = (9-3)/(2-6)
                                             = 6/-4
                                             = 3/-2 ------------(2)
Multiplying (1) and (2) we get, (2/3)(3/-2)
                              = -1

As the product of the slopes is -1, the lines are perpendicular .

==> the lines intersect  at right angle
==> the given points are the vertices of a right triangle 

good luck!!!

dolly