Determine whether the equation represent a circle or not : `5x^2 + 5y^2 + 4x - 8y - 16=0`

Determine whether the equation represent a circle or not : x^2 + y^2 + 6x - 8y + 50 = 0

Determine whether the equation represent a circle or not : 5x^2 + 5y^2 + 2xy + 4x-y+2=0

Determine whether the equation represent a circle or not : 3x^2 - 3y^2 + 4x-6y+ 10=0

Determine whether the equation represent a circle, a point or no circle : x^2 + y^2 +x-y=0

Determine whether the equation represent a circle, a point or no circle : x^2 + y^2 - 6x - 8y+25=0

Determine whether the equation represent a circle, a point or no circle : x^2 + y^2 + 2x + 10y + 26=0

Determine whether the equation represent a circle, a point or no circle : 2x^2 + 2y^2 -24x + 8y+120 = 0

Examine whether the following equation represents a circle or not : 4x^2 + 4y^2 + 12x + 8y+40=0

(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.

Identify , whether the following equation represent a straight line , parabola or circle: x^(2) + y^(2) =16