Q.
Let the position vectors of the points A,B and C be a,b and c, respectively. Let Q be the point of intersection of the medians of the ΔABC. Then, QA+QB+QC is equal to
Since, O is the intersecting point of all the medians of △ABC.
Hence, Q=3a+b+c
Now, dQA=a−3a+b+c =32a−b−c
{ Similarly, QB=32b−a−c
and QC=32c−a−b
Hence, QA+QB+QC=32a−b−c +32b−a−c+32c−a−b=0