A. 2x2+2y2-x-7y=0

B. 9x2+9y2-14x-30y+16=0

C. 9x2+9y2-52x+46y+105=0

D. x2+y2+8x-2y+1=0

The length of the intercept made by the circle x^{2}+y^{2}+10x-12y-13=0 on y-axis is

The angle between a pair-of tangents drawn from a point P to the circle x^{2}+y^{2}+4x-6y+9sin^{2}α+13cos^{2} α=0 is 2α.The equation of the locus of the point P is

The equation of the circle with centre at (-3, 4) and touching y-axis is

The centre of the circle (1+m^{2})(x^{2}+y^{2})-2cx-2cmy=0 is

The equation of the circle which cuts orthogonally the three circles x^{2}+y^{2}+4x+2y+1=0, 2x^{2}+2y^{2}+8x+6y-3=0 , x^{2}+y^{2}+6x-2y-3=0 is