5. An ellipse has a vertex at [tex]\((0, -7)\)[/tex], a co-vertex at [tex]\((4, 0)\)[/tex], and a center at the origin. Which equation represents the ellipse?

A. [tex]\(\frac{x^2}{49} + \frac{y^2}{16} = 1\)[/tex]

B. [tex]\(\frac{x^2}{4} + \frac{y^2}{7} = 1\)[/tex]

C. [tex]\(\frac{x^2}{7} + \frac{y^2}{4} = 1\)[/tex]

D. [tex]\(\frac{x^2}{16} + \frac{y^2}{49} = 1\)[/tex]



Answer :

To find the equation of the ellipse given the vertex, co-vertex, and center, let's follow these steps:

1. Identify the lengths of the semi-major and semi-minor axes:
- The vertex is at [tex]\((0, -7)\)[/tex]. This point indicates the end of the semi-major axis along the y-axis because the major axis is the longest diameter of the ellipse.
- The co-vertex is at [tex]\((4, 0)\)[/tex]. This point indicates the end of the semi-minor axis along the x-axis.

2. Calculate the lengths of the semi-major and semi-minor axes:
- The semi-major axis length ([tex]\(a\)[/tex]) is the absolute distance from the center to the vertex: [tex]\(a = |-7 - 0| = 7\)[/tex].
- The semi-minor axis length ([tex]\(b\)[/tex]) is the absolute distance from the center to the co-vertex: [tex]\(b = |4 - 0| = 4\)[/tex].

3. Write the standard form of the ellipse equation centered at the origin:
The standard form of an ellipse equation centered at the origin [tex]\((0, 0)\)[/tex] is:
[tex]\[ \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1 \][/tex]
Since [tex]\(a = 7\)[/tex] and [tex]\(b = 4\)[/tex], we substitute [tex]\(a^2\)[/tex] and [tex]\(b^2\)[/tex]:
[tex]\[ a^2 = 7^2 = 49 \][/tex]
[tex]\[ b^2 = 4^2 = 16 \][/tex]

4. Substitute these values into the standard form of the ellipse equation:
[tex]\[ \frac{x^2}{49} + \frac{y^2}{16} = 1 \][/tex]

Therefore, the correct equation of the ellipse is:
[tex]\[ \frac{x^2}{49} + \frac{y^2}{16} = 1 \][/tex]

By comparing with the given options, the correct answer is:
[tex]\[ \frac{x^2}{49} + \frac{y^2}{16} = 1 \][/tex]