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1)

 In a quadrilateral  PQRS, A divides SR in the ratio 1:3  and B is the mid-point of PR . If 3SR-QR-3PS-PQ=k AB, then k=


A) 2

B) 4

C) 6

D) 8

Answer:

Option D

Explanation:

Given PQRS a  quadrilateral  A divides SR  in the ratio 1:3 and B is the mid point PR.

 482021641_m6.PNG

Let the position vector of P,Q, R, S, A , B arep,q,r,s,a and b respectively

    SR=r-s ;QR=r-q             

              PS=s-p, PQ=q-p

AB=b-a

  a=3s+r4;b=p+r2

Now, 3SE-QR-3PS-PQ=KAB

 3(r-s)-(r-q)-3(s-p)-(q-p)=k(b-a)

  3r-3s-r+q-3s+3p-q+p=k

  (p+r23s+r4)

 =2r6s+4p=k(2p+2r3sr4)

 =8r24s+16p=2kp+2kr3ks

  k=8