Paragraph: Tangents are drawn from the point $P(3,4)$ to the ellipse $\frac{x^2}{9}+\frac{y^2}{4}=1$…

Paragraph: Tangents are drawn from the point $P(3,4)$ to the ellipse $\frac{x^2}{9}+\frac{y^2}{4}=1$ touching the ellipse at points $A$ and $B$. Question: The equation of the locus of the point whose distance from the point $P$ and the line $A B$ are equal, is
  1. $9 x^2+y^2-6 x y-54 x-62 y + 241=0$
  2. $x^2+9 y^2+6 x y-54 x+62 y - 241=0$
  3. $9 x^2+9 y^2-6 x y-54 x-62 y - 241=0$
  4. $x^2+y^2-2 x y+27 x+31 y - 120=0$

Solution

Equation of $A B$ is $y-0=-\frac{1}{3}(x-3)$ $ \begin{gathered} x+3 y-3=0 \\ |x+3 y-3|^2=10\left[(x-3)^2+(y-4)^2\right] \end{gathered} $ (Look at coefficient of $x^2$ and $y^2$ in the answers)

Asked in: JEE Advanced 2010 (Paper 2)

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