Hi there! The centre of this circle is (1, -1) and the radius is 2.
The standard form of a circle's formula is
[tex](x - a) {}^{2} + ( {y - b)}^{2} = r {}^{2} [/tex]
With a and b representing the coordinates of the centre and r representing the radius of the circle. Since in this situation r^2 equals 4, the radius (r) has to be 2.
