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TS EAMCET · Maths · Pair of Lines

The angle between the pair of straight lines formed by joining the points of intersection of \(x^2+y^2=4\) and \(y=3 x+c\) to the origin is a right angle. Then \(c^2\) is equal to

  1. A \(20\)
  2. B \(13\)
  3. C \(1 / 5\)
  4. D \(5\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(20\)

Step-by-step Solution

Detailed explanation

Since, the angle is right angle. \(\therefore\) Homogenising, \(x^2+y^2=4\left(\frac{y-3 x}{c}\right)^2\) \(\Rightarrow \quad c^2\left(x^2+y^2\right)=4\left(y^2+9 x^2-6 x y\right)\) These lines are perpendicular. \(\therefore\) coefficient of \(x^2+\) coefficient of \(y^2=0\)…