The ellipse is centered at the origin and has a horizontal axis of length 26 and a vertical axis of length 12. What is it's equation ?

The ellipse is centered at the origin and has a horizontal axis of length 26 and a vertical axis of length 12 What is its equation class=
The ellipse is centered at the origin and has a horizontal axis of length 26 and a vertical axis of length 12 What is its equation class=