Question

X2+y2-4+2y-11=0 what are the center and radius of the circle?

Answer 1

`x^2 + y^2 - 4x + 2y - 11 = 0`

You need to complete the square for both x and y.


`x^2 - 4x + y^2 + 2y = 11`


`x^2 - 4x + 4 + y^2 + 2y + 1 = 11 + 4 + 1`


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


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

The center is (2, -1).
The radius is 4.