Question:

The radical centre of the system of circles, \[ x^2 + y^2 + 4x + 7 = 0,\quad 2(x^2 + y^2) + 3x + 5y + 9 = 0 \] and \(x^2 + y^2 + y = 0\) is

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Radical center = solve pairwise subtractions of circle equations.
Updated On: Apr 16, 2026
  • \((-2,-1)\)
  • \((1,-2)\)
  • \((-1,-2)\)
  • None of these
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The Correct Option is A

Solution and Explanation

Concept: Radical center = intersection of radical axes.

Step 1:
Subtract equations.
Between first and second: \[ x^2+y^2+4x+7 - [2(x^2+y^2)+3x+5y+9]=0 \] \[ \Rightarrow -x^2 -y^2 + x -5y -2=0 \]

Step 2:
Subtract first and third.
\[ (x^2+y^2+4x+7)-(x^2+y^2+y)=0 \Rightarrow 4x - y + 7=0 \]

Step 3:
Solve.
Solving gives: \[ (-2,-1) \]
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