Equation of circle
`x^(2)+y^(2)+2x+4y-1=0`
Comparing with the general equation of the circle
`x^(2) + y^(2) +2gx + 2fy +c = 0`
`2g = 2,2f =4 and c = -1`
`rArr g = 1, f=2 and c = -1`
`:.` Radius of circle `= sqrt(g^(2)+f^(2)-c)`
`= sqrt((1)^(2)+(2)^(2)-(-1))`
`sqrt(1+4+1)`
`=sqrt(6)` units
And centre of circle `=(-g,-f)=(-1,-2)`.
