Question 1170502
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The endpoints of the major axis are (-9,0) and (9,0), so the center of the ellipse is (0,0) and the semi-major axis is 9.  The equation is then of the form<br>
{{{x^2/a^2+y^2/b^2 = 1}}}<br>
a is the semi-major axis and b is the semi-minor axis; a and b are related by<br>
{{{c^2 = a^2-b^2}}}<br>
where c is the distance from the center to each focus.<br>
Since the distance between the two foci is 8, the distance from the center to each focus is 4.<br>
So {{{c^2 = a^2-b^2}}}, with a=9 and c=4.  a^2=81; use that to determine b^2.  Then plug the a^2 and b^2 numbers into the equation.<br>