Answer:
The curve is a circle of radius 9 centered at the point (0,9) and the equation is

Explanation:
Proceed as follows:

Take
. Then

Multiply both side by
. Then

Use the following substitution
. Then

By cancelling out x on both sides we get the following equation
or

Recall that given a expression of the form
we can complete the square by adding an substracting the amount
. So, we get
. In our case, we will complete the square for y, then
. Then
or
.
Recall that the equation of a circle is given by
where (h,k) is the center of the circle and r is the radius. In our case we have h=0, k = 9 and r = 9. So it is a circle of radius 9 centered at the point (0,9)