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The centre of the circle, which cuts orthogonally each of the three circles

\mathrm{x^2+y^2+2 x+17 y+4=0, \quad x^2+y^2+7 x+6 y+11=0} and \mathrm{x^2+y^2-x+22 y+3=0} is

Option: 1

(3,2)


Option: 2

(1,2)


Option: 3

(2,3)


Option: 4

(0,2)


Answers (1)

Let the circle is \mathrm{x^2+y^2+2 g x+2 f y+c=0}           \mathrm{.....(i)}

Circle (i) cuts orthogonally each of the given three circles. Then according to condition

\mathrm{2 g_1 g_2+2 f_1 f_2=c_1+c_2}

\mathrm{2 g+17 f=c+4}                                                   \mathrm{.....(ii)}

\mathrm{7 g+6 f=c+11}                                                   \mathrm{.....(iii)}

\mathrm{-g+22 f=c+3}                                                 \mathrm{.....(iv)}

On solving (ii), (iii) and (iv), \mathrm{g=-3, f=-2}. Therefore, the centre of the circle \mathrm{(-g,-f)=(3,2)}

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Kshitij

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