MCQ
The equation of the tangents drawn at the ends of the major axis of the ellipse $9{x^2} + 5{y^2} - 30y = 0$, are
  • A
    $y = \pm 3$
  • B
    $x = \pm \sqrt 5 $
  • $y = 0,\;y = 6$
  • D
    None of these

Answer

Correct option: C.
$y = 0,\;y = 6$
c
(c) Change the equation $9{x^2} + 5{y^2} - 30y = 0$ in standard form $9{x^2} + 5({y^2} - 6y) = 0$

==> $9{x^2} + 5({y^2} - 6y + 9) = 45$

==> $\frac{{{x^2}}}{5} + \frac{{{{(y - 3)}^2}}}{9} = 1$

$\because {a^2} < {b^2},$ so axis of ellipse on $y$ - axis.

At $y$ axis, put $x = 0$, so we can obtained vertex.

Then $0 + 5{y^2} - 30y = 0$

$y = 0,\,\,y = 6$

Therefore, tangents of vertex $y = 0,\,\,\,y = 6$.

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