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Find the equation of the circle concentric with the circle x2 + y2 + 4x + 6y + 11 = 0 and passing through the point P(5, 4). |
Answer» Since circles are concentric, which means circles have common centre and different radii. Equation of given circle, x2 + y2 + 4x + 6y + 11 = 0 The concentric circle will have the equation x2 + y2 + 4x + 6y + d = 0 ….(1) As it passes through P(5, 4), Put x = 5 and y = 4 52 + 42 + 20 + 24 + d= 0 25 + 16 + 20 + 24 + d = 0 d = – 85 Equation (1) ⇒ x2 + y2 + 4x + 6y – 85 = 0 Which is required equation. |
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