The general form for a circle is (x - h)^2 + (y - k)^2 = r^2, where (h, k) represent the centre and r represent the radius.
With centre (7, -9) and radius 3, we can simply substitute it into our form:
(x - 7)^2 + (y + 9)^2 = 3^2
(x - 7)^2 + (y + 9)^2 = 9