Straight Line and Pair of Straight Lines 1 Question 38

38. If P=(1,0),Q=(1,0) and R=(2,0) are three given points, then locus of the points satisfying the relation SQ2+SR2=2SP2, is

(1988,2M)

(a) a straight line parallel to X-axis

(b) a circle passing through the origin

(c) a circle with the centre at the origin

(d) a straight line parallel to Y-axis

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Solution:

  1. Let the coordinate of S be (x,y).

SQ2+SR2=2SP2(x+1)2+y2+(x2)2+y2=2[(x1)2+y2]x2+2x+1+y2+x24x+4+y2=2(x22x+1+y2)2x+3=0x=32

Hence, it is a straight line parallel to Y-axis.



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