MCQ
For the ellipse $12\text{x}^2+4\text{y}^2+24\text{x}-16\text{y}+25=0$
  • A
    centre is (-1, 2)
  • B
    lengths of the axes are $\sqrt{3}$ and 1
  • C
    eccentricity $=\sqrt{\frac{2}{3}}$
  • D
    all of these.

Answer

Disclaimer : The equation should be $12\text{x}^2+4\text{y}^2+24\text{x}-16\text{y}+24=0$ instead of $12\text{x}^2+4\text{y}^2+24\text{x}-16\text{y}+25=0.$

  1. All of these

Solution:

$12\text{x}^2+4\text{y}^2+24\text{x}-16\text{y}+24=0$

$\Rightarrow12\big(\text{x}^2+2\text{x}\big)+4\big(\text{y}^2-4\text{y}\big)=-24$

$\Rightarrow12\big(\text{x}^2+2\text{x}+1\big)+4\big(\text{y}^2-4\text{y}+4\big)=-24+12+16$

$\Rightarrow12\big(\text{x}+1\big)^2+4\big(\text{y}-2\big)^2=4$

$\Rightarrow\frac{(\text{x}+1)^2}{3}+\frac{(\text{y}-2)^2}{1}=1$

So, the centre is a $(-1,\ 2).$

Here, $\text{a}=\sqrt{3}$ and $\text{b}=1$

The lengths of the axes are $\sqrt{3}$ and 1.

Now, $\text{e}=\sqrt{1-\frac{\text{b}62}{\text{a}^2}}$

$\text{e}=\sqrt{1-\frac{1}{3}}$

$\Rightarrow\text{e}=\sqrt{\frac{2}{3}}$

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