Question 260136
Given:
{{{4x^2+4y^2 = 81}}} determine the center and the radius.
Let's first get your equation into the standard form for a circle:
{{{(x-h)^2+(y-k)^2 = r^2}}} where the center is at (h, k) and the radius is r.
{{{4x^2+4y^2 = 81}}} Divide both sides by 4.
{{{x^2+y^2 = 20.25}}} This is now in standard form, so h = 0, k = 0, and {{{r^2 = 20.25}}} and {{{r = 4.5}}}
The center is at (0, 0) and the radius is r = 4.5