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Vector Algebra

Question
CBSEENMA12034029

Find the position vector of a point R which divides the line joining straight P left parenthesis 3 straight a with rightwards arrow on top space minus space 2 space straight b with rightwards arrow on top right parenthesis space and space straight Q left parenthesis straight a with rightwards arrow on top space plus space straight b with rightwards arrow on top right parenthesis in the ratio 2 : 1 
(i) internally and (ii) externally.

Solution
Given points are straight P left parenthesis 3 straight a with rightwards arrow on top space minus space 2 straight b with rightwards arrow on top right parenthesis comma space space straight Q left parenthesis straight a with rightwards arrow on top space plus space straight b with rightwards arrow on top right parenthesis
(i) The position vector of the point R dividing the join of P and Q internally in the 
  ratio  2 : 1 is

  
(ii) The  position vector of the point R dividing the join of P and Q externally in the ratio 2 : 1 is