Vertex problem

daleross9

New member
Joined
Nov 21, 2005
Messages
8
Can someone help me with this?

A vertex of
x^2/49 + y^2/25 = 1 is which of the following?

(5, 0)
(4, 0)
(0, -7)
(0, -5)
(7, 5)
(7, 0)
None of these


- Sir Dale Ross
 
Don't you have a formula for the vertices of an ellipse? Just plug into that.

If you are confused regarding how to use the formula, please reply showing the formula you have and how you've tried to use it to find the solution. Thank you.

Eliz.
 
I am not sure if I am right, but wouldn't it be (7, 5) ? Someone smarter can tell me if I am wrong. Just trying to help Dale!
 
Since the center is at the origin, the vertices will have to be on the x- and/or y-axes. (I say "and/or" depending on how the book defined "vertices"; they may just be the endpoints of the major axis, not the minor).

The center-axis formula for an ellipse is, I believe, something along the lines of the following:

. . . . .\(\displaystyle \Large{\frac{(x\mbox{ }-\mbox{ }h)^2}{a^2}\mbox{ }+\mbox{ }\frac{(y\mbox{ }-\mbox{ }k)^2}{b^2}\mbox{ }=\mbox{ }1}\)

...where the center is at (x, y) = (h, k). The book should give some relationship (very nice and neat) between the values "a" and "b" and the lengths of the major and minor axes. From this information, the vertices should be easily determined.

Eliz.
 
Try plugging that into the equation:

. . . . .(0)<sup>2</sup>/49 + (-7)<sup>2</sup>/25 ?=? 1

. . . . .0 + 49/25 ?=? 1

. . . . .49/25 ?=? 1

So the point (0, -7) doesn't actually lie on this particular ellipse. But you're on the right track....

Eliz.
 
Since neither (7, 5) nor (0, -1) lies on the curve, neither would be a solution.

Note to original poster: Please do not attempt to find the solution to your exercise by "factoring". Use the given form of the equation and the information you can read from it.

Eliz.
 
The posting from mad_mathematician should be deleted. (NOTE FROM TED: It has been.)
It is so wrong as to harmful to a reader.
Note that s/he factored the sum of two squares as if it were a difference.
mad_mathematician should be changed to sad_mathematician or better yet bad_mathematician.
 
pka said:
The posting from mad_mathematician should be deleted.
I don't know who this guy is, but he's posting really, really wrong stuff all over the place. I hope we have tutors online throughout the day to help correct any difficulties his posts may cause the students.

Oops! My hearing aid is beeping. Gotta change the battery. Be back in a bit....

Eliz.
 
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