" e) If the circle "x^(2)+y^(2)-4x+6y+a=0" has radius "4," find "a

If the circle x^(2)+y^(2)-4x+6y+a = 0 has radius 4 then find a.

Find the equation of the circle which is concentric with the circle x^(2) + y^(2) - 6x - 4y- 3 = 0 , and has radius 5.

The radius of the circle x ^(2) +y^(2) +4x+6y+13=0 is-

(i) Find the equation of a circle , which is concentric with the circle x^(2) + y^(2) - 6x + 12y + 15 = 0 and of double its radius. (ii) Find the equation of a circle , which is concentric with the circle x^(2) + y^(2) - 2x - 4y + 1 = 0 and whose radius is 5. (iii) Find the equation of the cricle concentric with x^(2) + y^(2) - 4x - 6y - 3 = 0 and which touches the y-axis. (iv) find the equation of a circle passing through the centre of the circle x^(2) + y^(2) + 8x + 10y - 7 = 0 and concentric with the circle 2x^(2) + 2y^(2) - 8x - 12y - 9 = 0 . (v) Find the equation of the circle concentric with the circle x^(2) + y^(2) + 4x - 8y - 6 = 0 and having radius double of its radius.

Find the radius of the circle x^(2)+y^(2)-4x-6y+12=0

The radius of the circle x^(2) + y^(2) + 4x - 6y + 12 = 0 is

The radius of the circle x^(2) + y^(2) + 4x - 6y + 12 = 0 is

Find the equation of the circle concentric with the circle x^(2) + y^(2) - 4x + 6y + 4 = 0 and passing through the point (2, -2).