Question 744465
One might assume that your given "vertex" is on the major axis.  Seems like it makes sense.  The distance from -2 to +7 is 9.  Your 'a' value is then 9.  Looking at this vertex and the center point of the ellipse, 9 being with the major axis, your a=9 goes with the x term.  


Final answer is:
{{{(1/(9^2))(x+2)^2+(1/(6^2))(y-3)^2=1}}}