Answer:
C
Step-by-step explanation:
The equation of a circle in standard form is
(x - h)² + (y - k)² = r²
where (h, k) are the coordinates of the centre and r is the radius
Given x² + y² + 4x - 10y + 20 = 0
Collect x and y terms and subtract 20 from both sides. that is
x² + 4x + y² - 10y = - 20
To obtain standard form use the method of completing the square
add ( half the coefficient of the x/y term )² to both sides
x² + 2(2)x + 4 + y² + 2(- 5)y + 25 = - 20 + 4 + 25
(x + 2)² + (y - 5)² = 9 ← in standard form
with centre = (- 2, 5) and r = [tex]\sqrt{9}[/tex] = 3 → C
