10 CBSE Co-ordinate Geometry Ex. 7.1 sum ( question) no. 3. After getting the distances using distance formula. The sum is about how to decide whether the points are collinear. Finding square roots of 5, 212 & 265 by long division will take lot of time, so the alternative method which is the best short cut.
You may even find by geometrical construction 9 CBSE by taking suitable scale (by dividing by a suitable perfect square say 25). However this method also is time-consuming and needs lot of practice to master it.
