MHT CET 2017 Math Solved Paper

(c) Consider p, q, r, s, m and n are the position vectors of P, Q, R, S, M and N be respectively.
As, M and N are mid-points of PQ and RSrespectively
So, m =

p+q

2

and n =

r+s

2

...(i)
Now, PS + QR
= s - p + r - q = (r + s) (p + q)
= 2n - 2m = 2MN [From eq. (i)]