Question 935933
Here is some of the information:


a=4, center is (2,1), and the distance from center to either focus is c=3.  You want the value for b, and there is a relationship among a, b, and c.
{{{c^2=a^2-b^2}}}.


standard form of a general unrotated two dimensional ellipse is  {{{(x-h)^2/a^2+(y-k)^2/b^2=1}}} for a center at (h,k).