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10-2. Parabola, Ellipse, Hyperbola
easy
If the centre, one of the foci and semi-major axis of an ellipse be $(0, 0), (0, 3)$ and $5$ then its equation is
A
$\frac{{{x^2}}}{{16}} + \frac{{{y^2}}}{{25}} = 1$
B
$\frac{{{x^2}}}{{25}} + \frac{{{y^2}}}{{16}} = 1$
C
$\frac{{{x^2}}}{9} + \frac{{{y^2}}}{{25}} = 1$
D
None of these
Solution
(a) Centre $(0,0)$, focus $(0,3)$, $b = 5$
Focus $(0,3)$ ==> $be = 3$
==> $e = 3/5$ ==> $a = b\sqrt {1 – {e^2}} = 4$
Hence the required equation is $\frac{{{x^2}}}{{16}} + \frac{{{y^2}}}{{25}} = 1$.
Standard 11
Mathematics