What is the equation of the circle in general form?
x2+y2−2x−8y−47=0
x² + y² + 2x + 8y + 9 = 0
x2+y2+2x+8y−47=0
x2+y2−2x−8y+9=0
The center is (1,4)
The radius is 8
So...we have
(x-1)^2 + (y - 4)^2 = 8^2 implify
x^2 - 2x + 1 + y^2 - 8y + 16 = 64
x^2 + y^2 -2x - 8y + 17 = 64 subtract 64 from both sides
x^2 + y^2 - 2x - 8y - 47 = 0
+12 
