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COMEDK · Maths · 12. Circle

The radius and centre of circle which equation is \(3 x^2+3 y^2+6 x+12 y+5=0\) is

  1. A \((-3,-4), \sqrt{20}\)
  2. B \((3,4), \sqrt{20}\)
  3. C \((-1,-2), 5 \sqrt{\frac{2}{3}}\)
  4. D \((1,2), 5 \sqrt{\frac{2}{3}}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \((-1,-2), 5 \sqrt{\frac{2}{3}}\)

Step-by-step Solution

Detailed explanation

If equation of circle is \(x^2+y^2+2 g x+2 f g+c=0\) Then, centre \(=(-g,-f)\) \(\begin{aligned} & \text { Radius }=\sqrt{g^2+f^2-c} \\ & \Rightarrow x^2+y^2+2 x+4 y+\frac{5}{3}=0 \end{aligned}\)…