MCQ
A point ratio of whose distance from a fixed point and line $x = 9/2$ is always $2 : 3$. Then locus of the point will be
  • A
    Hyperbola
  • Ellipse
  • C
    Parabola
  • D
    Circle

Answer

Correct option: B.
Ellipse
b
(b) In question, $PS = \frac{2}{3}PM$ (Given)

Focus $S( - 2,\,0)$,

Equation of directrix $2x - 9 = 0$

${(PS)^2} = \frac{4}{9}{(PM)^2}$

==> ${(h + 2)^2} + {(k)^2} = \frac{4}{9}{\left( {\frac{{2h - 9}}{2}} \right)^2}$

==> $9[{(h + 2)^2} + {(k)^2}] = \frac{{4{{(2h - 9)}^2}}}{4}$

==> $9{h^2} + 9{k^2} + 36h + 36 = 4{h^2} + 81 + 36h$

==> $\frac{{5{h^2}}}{{45}} + \frac{{9{k^2}}}{{45}} = 1$

==> $\frac{{{h^2}}}{9} + \frac{{{k^2}}}{5} = 1$ 

Locus of point $P(h, k)$ is $\frac{{{x^2}}}{9} + \frac{{{y^2}}}{5} = 1$, which is an ellipse

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