Find the center and the radius of the circle x2y22x6y90Solut

Find the center and the radius of the circle.    
x^2+y^2+2x-6y+9=0

Solution

x² + y² + 2x - 6y + 9 = 0

==> x² + 2x + y² - 6y + 9 = 0

==> x² + 2(x)(1) + 1² - 1² + y² - 2(y)(3) + 3² - 3² + 9 = 0

==> (x + 1)² + (y - 3)² - 1 = 0

==> (x + 1)² + (y - 3)² = 1

Comparing by general form (x - h)² + (y - k)² = r²

==> Centre = (h , k) = (-1 , 3)

Radius r = 1