Find the equation of the ellipse in the following cases: The ellipse passes through (1, 4) and (- 6, 1)
Find the equation of the ellipse in the following cases: The ellipse passes through (1, 4) and (- 6, 1)

The ellipse passes through

    \[\left( 1,\text{ }4 \right)\text{ }and\text{ }\left( -\text{ }6,\text{ }1 \right)\]

Given:

The points

    \[\left( 1,\text{ }4 \right)\text{ }and\text{ }\left( -\text{ }6,\text{ }1 \right)\]

Now let us find the equation to the ellipse.

We know that the equation of the ellipse whose axes are x and y – axis is given as

    \[\ldots .\text{ }\left( 1 \right)\]

RD Sharma Solutions for Class 11 Maths Chapter 26 – Ellipse - image 61

Let us substitute the point (1, 4) in equation (1), we get

RD Sharma Solutions for Class 11 Maths Chapter 26 – Ellipse - image 62

    \[{{b}^{2}}~+\text{ }16{{a}^{2}}~=\text{ }{{a}^{2}}~{{b}^{2}}~\ldots .\text{ }\left( 2 \right)\]

Let us substitute the point (-6, 1) in equation (1), we get

RD Sharma Solutions for Class 11 Maths Chapter 26 – Ellipse - image 63

    \[{{a}^{2}}~+\text{ }36{{b}^{2}}~=\text{ }{{a}^{2}}{{b}^{2}}~\ldots .\text{ }\left( 3 \right)\]

Let us multiply equation (3) by 16 and subtract with equation (2), we get

    \[(16{{a}^{2}}~+\text{ }576{{b}^{2}})\text{ }\text{ }({{b}^{2}}~+\text{ }16{{a}^{2}})\text{ }=\text{ }(16{{a}^{2}}{{b}^{2}}-\text{ }{{a}^{2}}{{b}^{2}})\]

    \[575{{b}^{2}}~=\text{ }15{{a}^{2}}{{b}^{2}}\]

Or,

    \[15{{a}^{2}}~=\text{ }575\]

    \[{{a}^{2}}~=\text{ }575/15\]

So,

    \[=\text{ }115/3\]

So from equation (2),

RD Sharma Solutions for Class 11 Maths Chapter 26 – Ellipse - image 64

So the equation of the ellipse can be given as

RD Sharma Solutions for Class 11 Maths Chapter 26 – Ellipse - image 65

    \[3{{x}^{2}}~+\text{ }7{{y}^{2}}~=\text{ }115\]

∴ The equation of the ellipse is

    \[3{{x}^{2}}~+\text{ }7{{y}^{2}}~=\text{ }115\]