The locus of the centers of the circles which cut the circles x2 + y2 + 4x - 6y + 9 = 0 and x2 + y2 - 5x + 4y - 2 = 0 orthogonally is : 

(A) 9x + 10y - 7 = 0 

(B) x - y + 2 = 0 

(C) 9x - 10y + 11 = 0 

(D) 9x + 10y + 7 = 0

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1 Answers

(C) 9x - 10y + 11 = 0 

Let out circle be x2 + y2 + 2gx + 2fy + c = 0

conditions 2(– g) (–2) + 2( – f ) (3) = c + 9

and 2(– g) (5/2) + 2( – f ) (–2) = c – 2

∴ ag – 10 f = 11

∴ locus of centre 9x – 10y + 11 = 0

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