EllipseHardBloom L3

Question

If the focus, centre and eccentricity of an ellipse are respectively $(3,4)(2,3)$ and $\frac{1}{2}$, then its equation is given by:

Options

A.$\frac{(x + y - 5)^{2}}{16} + \frac{(x - y + 1)^{2}}{12} = 1$
B.$\frac{(x - y + 1)^{2}}{16} + \frac{(x + y - 5)^{2}}{12} = 1$
C.$\sqrt{(x - 3)^{2} + (y - 4)^{2}} + \sqrt{(x - 2)^{2} + (y - 1)^{2}} = 4\sqrt{2}$
D.$\sqrt{(x - 3)^{2} + (y - 4)^{2}} + \sqrt{(x - 1)^{2} + (y - 2)^{2}} = 4\sqrt{2}$

Solution

Sol. Equation of major axis is $y = x + 1$

Equation of minor axis is $x + y = 5$

$$\begin{matrix} ae & \ = \sqrt{(4 - 3)^{2} + (3 - 2)^{2}} \\ & \ = \sqrt{2} \Rightarrow a = 2\sqrt{2} \\ b^{2} & \ = a^{2} - a^{2}e^{2} = 8 - 2 = 6 \Rightarrow b = \sqrt{6} \end{matrix}$$

Equation of ellipse is

$$\frac{\left( \frac{x + y - 5}{\sqrt{2}} \right)^{2}}{(2\sqrt{2})^{2}} + \frac{\left( \frac{y - x - 1}{\sqrt{2}} \right)^{2}}{(\sqrt{6})^{2}} = 1$$

Also, its equation is

$$\sqrt{(x - 3)^{2} + (y - 4)^{2}} + \sqrt{(x - 1)^{2} + (y - 2)^{2}} = 2(2\sqrt{2})$$

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