Question 37458
This ellipse has a center at the origin.  That can be seen if you plot the intercepts.  Also you can see that the semi-major axis (a) is 4, and the semi-minor axis (b) is 2.  So we plug into the standard form of an ellipse to get:
(x^2)/(a^2) + (y^2)/(b^2) = 1
(x^2)/(4^2) + (y^2)/(2^2) = 1
(x^2) / 16 + (y^2) / 4 = 1
and we're done.