I have to write an equation in standard form for the ellipse with center (0,0) co-vertex (4,0) and focus (0,3) this really confuses me,

Question

tkhunny · Answer

Center at (0,0) -- This simplifies things a lot.
Focus at (0,3) -- Aha!!!!  There must be another focus at (0,-3)  ==> c = 3
Co-Vertex at (4,0) -- Aha!!!!  There must be another co-vertex at (-4,0) ==> b = 4

There is a relationship between 'a', 'b' and 'c' for an ellipse.  Do you know what it is?

anonymous · Answer

isnt it c^2=a^2+b^2?

tkhunny · Answer

It is important to be confident on this.  Please compare it to the formula for an hyperbola.  Make sure you know which is which.

For an ellipse, a > c!

anonymous · Answer

so  it would be y2/16+x^2/25=1?

tkhunny · Answer

I believe you have the 16 and 25 switched.  Look carefully at the vertices.  Where are they?  Which is a greater distance from the origin?