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Question: Answered & Verified by Expert
If a circle $S$ passing through the point $(3,4)$ cuts the circle $x^2+y^2=36$ orthogonally, then the locus of the centre of $S$ is
MathematicsCircleAP EAMCETAP EAMCET 2018 (22 Apr Shift 2)
Options:
  • A $x^2+y^2-6 x-8 y+11=0$
  • B $6 x+8 y-61=0$
  • C $x^2+y^2-8 x-6 y+11=0$
  • D $6 x+8 y+11=0$
Solution:
1475 Upvotes Verified Answer
The correct answer is: $6 x+8 y-61=0$
Let the circle is $x^2+y^2+2 g x+2 f y+c=0$, having centre $(-g,-f)$, since it passes through the point $(3,4)$


And circle is intersecting the other circle
$$
\begin{aligned}
& x^2+y^2=36 \text { orthogonally, so } \\
& \qquad 2 g(0)+2 f(0)=c-36
\end{aligned}
$$

From Eqs. (i) and (ii)
$$
-6 g-8 f=61,
$$
Now, on taking locus of point $(-g,-f)$, we are getting $6 x+8 y-61=0$.

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