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AP EAMCET · Maths · Circle

If the circles \(x^2+y^2-2 x-2 y-7=0\) and \(x^2+y^2+4 x+2 y+k=0\) cut orthogonally, then the length of their common chord is units

  1. A 2
  2. B 5
  3. C \(\frac{6}{\sqrt{13}}\)
  4. D \(\frac{12}{\sqrt{13}}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{12}{\sqrt{13}}\)

Step-by-step Solution

Detailed explanation

Since the given circles \[ x^2+y^2-2 x-2 y-7=0 \text { and } \] \(x^2+y^2+4 x+2 y+k=0\) cut orthogonally, then \[ (-2)(2)+(-2)(1)=k-7 \] \(\Rightarrow \quad-4-2=k-7 \Rightarrow k=1\) So, equation of common chord is \[ 6 x+4 y+8=0 \Rightarrow 3 x+2 y+4=0 \] \(\therefore\) Length…