Question

Circle.
x2 - 8x +y2 - 2y +1=0

Answer 1

r = 4

Explanation:

Answer 2

Center (4,1)

Radius r = 4

Explanation:

Complete the square to fill in the standard circle equation:

• 
  `(x-h)^2+(y-k)^2=r^2` , (h,k) is the center, r is the radius

`(x^2-8x+16) + (y^2-2y+1) = 16`

Use formula:
`x^2+2ax+a^2=(x+a)^2`

therefore,
`(x-4)^2+(y-1)^2=16`

(h,k) = (4,1)

r = 4