In Exercises 1–4, find the focus and directrix of each parabola with the given equation. Then match each equation to one of the graphs that are shown and labeled (a)–(d). x^2 = - 4y
Ch. 7 - Conic Sections

Chapter 8, Problem 3
Graph each ellipse and locate the foci. x2/9 +y2/36= 1
Verified step by step guidance1
Identify the standard form of the ellipse equation given: \(\frac{x^{2}}{9} + \frac{y^{2}}{36} = 1\). Here, \(a^{2}\) and \(b^{2}\) are the denominators under \(x^{2}\) and \(y^{2}\) respectively.
Determine which denominator is larger to identify the major axis. Since \(36 > 9\), the major axis is vertical, and \(a^{2} = 36\), so \(a = 6\). The minor axis corresponds to \(b^{2} = 9\), so \(b = 3\).
Plot the ellipse centered at the origin \((0,0)\) with vertices along the major axis at \((0, \pm a)\), which are \((0, \pm 6)\), and co-vertices along the minor axis at \((\pm b, 0)\), which are \((\pm 3, 0)\).
Calculate the focal distance \(c\) using the relationship \(c^{2} = a^{2} - b^{2}\). Substitute the values to find \(c^{2} = 36 - 9\).
Locate the foci on the major axis at points \((0, \pm c)\), which are \((0, \pm \sqrt{c^{2}})\). These points lie inside the ellipse along the vertical axis.

Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
10mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Standard Form of an Ellipse
The equation x²/a² + y²/b² = 1 represents an ellipse centered at the origin. Here, a² and b² are the denominators under x² and y², indicating the lengths of the semi-major and semi-minor axes. Identifying which denominator is larger helps determine the ellipse's orientation (horizontal or vertical).
Recommended video:
Graph Ellipses at Origin
Graphing an Ellipse
To graph an ellipse, plot the center at the origin, then mark points a units along the major axis and b units along the minor axis. Connect these points smoothly to form the ellipse. This visual representation helps understand the shape and size of the ellipse based on its equation.
Recommended video:
Graph Ellipses NOT at Origin
Locating the Foci of an Ellipse
The foci are two fixed points inside the ellipse along the major axis, found using c² = |a² - b²|, where c is the distance from the center to each focus. Knowing the foci is essential for understanding ellipse properties, such as the sum of distances from any point on the ellipse to the foci being constant.
Recommended video:
Foci and Vertices of an Ellipse
Related Practice
Textbook Question
1112
views
Textbook Question
Find the standard form of the equation of the ellipse satisfying the given conditions. Foci: (-4,0), (4,0); Vertices: (-5,0) (5,0)
2254
views
1
rank
1
comments
Textbook Question
Graph each ellipse and locate the foci. x2/25 +y2/64 = 1
1036
views
Textbook Question
Find the vertices and locate the foci of each hyperbola with the given equation. Then match each equation to one of the graphs that are shown and labeled (a)–(d).
a. b. c. d.
y2/4−x2/1=1
875
views
Textbook Question
Graph the ellipse and locate the foci. 9x^2 + 4y^2 - 18x + 8y -23 = 0
1379
views
Textbook Question
In Exercises 1–4, find the focus and directrix of each parabola with the given equation. Then match each equation to one of the graphs that are shown and labeled (a)–(d). y^2 = - 4x
918
views
