Which of the following equations represent a circle and if so, find its centre and radius:
`x^2 +y^2 -x+2y - 3=0`.

In the following ,find the equation of the circle with:- centre (-2,3) and radius 4

Find the equations of the following curves in cartesian form. Wherever the curve is a circle, find its centre and radius : x= at^2, y=2at .

Find the centre and radius of the circle : 2x^2 + 2y^2- x=0 .

Find the equations of the following curves in cartesian form. Wherever the curve is a circle, find its centre and radius : x=1+2 cos alpha, y=3+2 sin alpha .

In the following ,find the equation of the circle with:-centre (0,2) and radius 2

Find the equations of the following curves in cartesian form. Wherever the curve is a circle, find its centre and radius : x= 1/2 t+1, y= 2t-1 .

Find the centre and radius of the circle : x^2 + y^2+ 8x + 10y- 8 =0 .

Find the centre and radius of the circle : x^2 + y^2- 4x- 8y- 45 = 0 .