Question

Find the coordinates of the foci for the ellipse:

(x + 3)2/9 + (y - 1)2/25 = 1

A. (3, -1) and (3, 5)
B. (-3, 3) and (-3, 1)
C. (-3, 5) and (-3, -3)
D. (1,1) and (-7,1)

Answer 1

http://www.mathopenref.com/ellipsefoci.html Check this out...should help you understand how to find it.

Answer 2

@Chris9k Nope still not able to figure out :/

Answer 3

You have your center at (-3, 1) that it is in standard form and you can pull that straight out of the formula of an ellipse. Do you see where that came from?

Answer 4

@Chris9k Yes I think so, did you get the -3 from multiplying the 3 and -1

Answer 5

You know y is your major axis because 25>9....a^2 =25. b^2 =9. Then you take the square root of your major axis squared minus your minor axis squared. That give you sqrt(5^2 - 3^2) = sqrt(25-9) = sqrt(16) = 4. The foci will be along the major axis which is the y-axis. You then + and - 4 from the y value of the center. (-3, 1+4) and (-3,1-4) = (-3,5) and (-3, -3).

Answer 6

I got the center from (x+3) part of the equation....that means the x-term of your center is -3. for the y-term of the center you go from (y-1) which means the y value of the center is +1...so (-3,1) for center.

Answer 7

@Chris9k Ooh Ok I got it, Thank You very much

Answer 8

Great! You're welcome.