Answer:
centre = (2, 4)
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 - 8y - 5 = 0
Rearrange the x/y terms together and add 5 to both sides
x² - 4x + y² - 8y = 5
Use the method of completing the square on both the x/y terms
add ( half the coefficient of the x/y terms )² to both sides
x² + 2(- 2)x + 4 + y² + 2(- 4)y + 16 = 5 + 4 + 16
(x - 2)² + (y - 4)² = 25 ← in standard form
with centre (2, 4) and r = [tex]\sqrt{25}[/tex] = 5
