Finding the radius of the circle is fairly straight forward. All you do is take the square of 36 which is 6 an that is your radius. The center is determined by the constants within the parenthesis. The 6 shifts the equation left 6 units on the x axis and the - 4 shifts the equation up 4 units along the y axis. So the center makes the value on the left equal 0, so that would be (-6,4). Hope this helps. This is what it looks like if the link works.