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TS EAMCET · Maths · Ellipse

For \(k>0\), the shortest distance from a point \(P(1, k)\) on the ellipse \(9 x^2+4 y^2-18 x+16 y-11=0\) to one of its directrix is

  1. A \(3-\sqrt{5}\)
  2. B \(3+\sqrt{5}\)
  3. C \(\frac{9}{\sqrt{5}}-3\)
  4. D \(\frac{9}{\sqrt{5}}-2\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\frac{9}{\sqrt{5}}-3\)

Step-by-step Solution

Detailed explanation

We, have, \(P(1, k)\) lies on ellipse \(\begin{aligned} & 9 x^2+4 y^2-18 x+16 y-11=0 \\ & \therefore \quad 9+4 k^2-18+16 k-11=0 \\ & \Rightarrow \quad 4 k^2+16 k-20=0 \\ & \Rightarrow \quad k^2+4 k-5=0 \\ & \Rightarrow \quad(k+5)(k-1)=0 \Rightarrow k=-5,1 \\ & \end{aligned}\)…