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Section 4.3 : Ellipses

3. Sketch the graph of the following ellipse.

\[4{\left( {x + 2} \right)^2} + \frac{{{{\left( {y + 4} \right)}^2}}}{4} = 1\]

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The first step here is to simply compare our equation to the standard form of the ellipse and identify all the important information. For reference purposes here is the standard form of the ellipse.

\[\frac{{{{\left( {x - h} \right)}^2}}}{{{a^2}}} + \frac{{{{\left( {y - k} \right)}^2}}}{{{b^2}}} = 1\]

To help with the comparison let’s rewrite our equation a little to make it look more like the standard form.

\[\frac{{{{\left( {x + 2} \right)}^2}}}{{\frac{1}{4}}} + \frac{{{{\left( {y + 4} \right)}^2}}}{4} = 1\]

In order to properly identify \(a\) and \(b\) the numbers need to be in the denominator. So, we needed to move the 4 from the numerator of the first term into a ¼ in the denominator.

Comparing our equation to this we can see we have the following information.

\[h = - 2\hspace{0.25in}k = - 4\hspace{0.25in}a = \frac{1}{2}\hspace{0.25in}b = 2\]
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With the information we found in the first step we can see that the center of the ellipse is \(\left( { - 2, - 4} \right)\).

The right most, left most, top most and bottom most points are then,

\[\begin{align*} & {\mbox{Right Most Point :}}\,\,\left( { - 1.5, - 4} \right)\\ & {\mbox{Left Most Point :}}\,\,\left( { - 2.5, - 4} \right)\\ & {\mbox{Top Most Point :}}\,\,\left( { - 2, - 2} \right)\\ & {\mbox{Bottom Most Point :}}\,\,\left( { - 2, - 6} \right)\end{align*}\]
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Here is a sketch of the ellipse including all the points we found above.

The graph of the ellipse with center \(\left( { - 2, - 4} \right)\).  The center is marked with a dot and the four points found above are marked and labeled on the ellipse.  They are the right most point \(\left( { - 1.5, - 4} \right)\), the left most point \(\left( { - 2.5, - 4} \right)\), the top most point \(\left( { - 2, - 2} \right)\) and the bottom most point \(\left( { - 2, - 6} \right)\).  The ellipse is long and narrow, being much taller than it is wide.