Q.

Let T be the line passing through the points  P(2,7)andQ(2,5). Let  F1 be the set of all pairs of circles (S1,S2) such that T is tangent to S1 at P and tangent to S2 at Q, and also such that S1&S2 touch each other at point, say, M. Let E1 be the set representing the locus of M as the pair (S1,S2)  varies in  F1. Let the set of all straight line segments joining a pair of distinct points of E1 and passing through the point  R(1,1) be  F2. Let  E2  be the set of the mid-points of the line segments in the set  F2. Then, which of the following statement(s) is (are) TRUE?

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a

The point  (12,1)  lies in E2

b

The point  (0,32) does NOT lie in  E1

c

The point (-2,7) lies in E1

d

The point (45,75)  does NOT lie in  E2

answer is B, D.

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Detailed Solution

detailed_solution_thumbnail

MN is radical axis and MN = NP = NQ
  locus of M is circle with centre N =N=P+Q2   and  r=NQ  or  NP=40
Question Image

Locus of M is circle centre (0,1) and radius  40, excluding points P and Q
x2+y22y=39 excluding points P and Q 
(2,7) is excluded from locus and  (0,32) does not lie in  E1
Locus of point in E2 is circle with diameter (0,1) and (1,1), excluding midpoints of chords passing through P or Q 
 x2x+(y1)2=0
(12,1) does not lie in E2 and (45,75) doesn’t lie in E2 since latter is midpoint of chord through P 

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