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1)

If one of the diameters of the circle, given by the equation  x2+y24x+6y12=0, is a chord of a circle S, whose centre is at (-3,2), then the radius of S is


A) 52

B) 53

C) 5

D) 10

Answer:

Option B

Explanation:

Given the equation of a circle is  x2+y24x+6y12=0, whose centre is (2,-3) and radius

    =22+(3)2+12=4+9+12=5

 Now , according to given information , we have the following figure

   x2+y24x+6y12=0

 Clarly, AOBC, as O is  mid-point of the  chord

1932020562_circ.JPG

Now, in ΔAOB , we have

OA=(32)2+(2+3)2 

  =25+25=50=52

and OB=5

   AB=OA2+OB2

50+25=75

  = 53