Q. The centre of the circle, which cuts orthogonally each of the three circles $x^{2} + y^{2} + 2x + 17y + 4 = 0$ and $x^{2} + y^{2} + 7x + 6y + 11 = 0¸x^{2} + y^{2} - x + 22y + 3 = 0$, is

A) (3, 2)
B) (1, 2)
C) (2, 3)
D) (0, 2)
Explanation

(a)
Let general equation of a circle is
$x^{2} + y^{2} + 2gx + 2fy + c = 0$ …(i)
If the circle (i) cuts orthogonally each of the given three circles
Then, condition is
$2g_{1}g_{2} = 2f_{1}f_{2} = c_{1} + c_{2}$
Applying the condition one by one, we get
$2g + 17f = c + 4$ …(ii)
$7g + 6f = c + 11$ …(iii)
And $- g + 22f = c + 3$ …(iv)
On solving Eqs. (ii), (iii) and (iv), we get
$g = - 3,\ f = - 2$
Therefore, the centre of the circle is (3, 2)

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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