An ellipse centered at (h, k) is (x − h)²/a² + (y − k)²/b² = 1. The larger denominator sits under the axis that is stretched. Conics as a set are in conic sections.
Center, then stretch
Read (h, k) the same way as a circle. If a² is under x and is larger than b², the ellipse is wider than it is tall. A circle is the special case a = b, in the equation of a circle.
Completing the square may be required first, in completing the square. Graphing a circle in Desmos is in graphing a circle in Desmos.
The bottom line
Center (h, k). Bigger denominator means the longer axis.
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