pusat dan jari-jari x^2+y^2+2x-10y+25=0

Lingkaran.

x² + y² + Ax + By + C = 0
x² + y² + 2x - 10y + 25 = 0

P(-1/2 A, -1/2 B)
= P(-1/2 (2), -1/2 (-10)) = P(-1, 5)

r = √(1/4 A² + 1/4 B² - C)
  = √[1/4 (2)² + 1/4 (-10)² - 25] = 1