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AP EAMCET · Maths · Ellipse

The foci of the ellipse \(9 x^2+25 y^2=225\) are

  1. A \(( \pm 4,0)\)
  2. B \(\left( \pm \frac{4}{5}, 0\right)\)
  3. C \(\left( \pm \frac{12}{5}, 0\right)\)
  4. D \(\left( \pm \frac{2}{5}, 0\right)\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(( \pm 4,0)\)

Step-by-step Solution

Detailed explanation

Ellipse is \(9 x^2+25 y^2=225\) \[ \begin{aligned} & \Rightarrow \frac{x^2}{25}+\frac{y^2}{9}=1, a=5, b=3 \\ & \therefore e=\sqrt{1-\frac{b^2}{a^2}}=\sqrt{1-\frac{9}{25}}=\frac{4}{5} \end{aligned} \] \(\therefore\) Foci are \(( \pm a e, 0) \equiv( \pm 4,0)\)