Question 972202
You learn to derive each of the two-dimensional conic sections and to put them into a standard form.  And then, you learn to recognize which conic section based on the form you see.  This one is an ellipse.


Divide yours by 36.


{{{x^2/18+y^2/36=1}}}


{{{graph(300,300,-8,8,-8,8,sqrt(36-2x^2),-sqrt(36-2x^2))}}}