Find the equation. of the circle concentric with the `x^2 +y^2 + 4x-8y-6=0` and having radius double of its radius.

The equation of the circle concentric with x^(2)+y^(2)-6x+4y-3=0 and having radius 5 is

Find the equation of the circle concentric with the circle 2x^2 + 2y^2 - 6x + 8y+1=0 and of double its area.

Find the equation of the circle which is concentric with the circle x^2 +y^2 - 4x+6y-3=0 and the double of its area.

Write the equation of the unit circle concentric with x^2+y^2-8x+4y-8=0.

Find the equation of the circle concentric with the circle x^2 + y^2 - 4x - 6y - 3 = 0 and which touches the y axis

Find the equation of the circle concentric with the circle x^2 +y^2 - 4x - 6y-9=0 and passing through the point (-4, -5)

(i) Find the equation of a circle concentric with the circle x^(2)+y^(2)-8x+6y-10=0 and passes through the point (-2,3). (ii) Find the equation of circle concentric with the circle x^(2)+y^(2)-4x-8y-6=0 and whose radius is three times the radius of this circle.

Find the equation of a circle concentric with the circle 2x^(2)+2y^(2)-6x+8y+1=0 and double of its area.

Find the equation of the circle concentric with the circle x^(2) + y^(2) - 8x + 6y -5 = 0 and passing through the point (-2, -7).

The equation of a circle concentric with the circle x^(2) + y^(2) - 6x + 12 y + 15 = 0 and double its area is