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Question: Answered & Verified by Expert
The number of possible common tangents that can be drawn to the circles x2+y2+4x-6y-3=0 and x2+y2+4x-2y+1=0 is
MathematicsCircleTS EAMCETTS EAMCET 2021 (04 Aug Shift 1)
Options:
  • A 4
  • B 3
  • C 1
  • D 0
Solution:
1770 Upvotes Verified Answer
The correct answer is: 1

Two circles given are x2+y2+4x-6y-3=0 & x2+y2+4x-2y+1=0

Now compare 1 with x2+y2+2gx+2hy+c=0 we get

2g=4g=2  &  2h=-6 h=-3

Centre of circle is given by -g,-h ,so C1-2,3 gives the centre of first circle

Similarly , C2-2,1 which gives centre of second circle.

Now, r1=4+9+3=4 & r2=4+1-1=2

C1C2=2 (by using distance formula)

r1-r2=C1C2

This is the case when a circle is touching another circle internally. So, there will be only one common tangent.

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