Which of the following equation represent circles? (iii) x`^2` + y`^2` + 2x + 4y + 6xy + 8 = 0

Which of the following equation represent circles? (ii) x ^2 + 4y ^2 + 2x + 12y + 6 = 0

Which of the following equation represent circles? (iv) x ^2 + y ^2 + 4x + 16y + 59 = 0

Which of the following equation represent circles? (i) 9x ^2 + 9y ^2 + 12x + 18y + 1 = 0

Does each of the following equation represent a circle? If so, find the centre and radius of the circle. (iii) 2x ^2 + y ^2 - 6x -8y - 11 = 0

Does each of the following equation represent a circle? If so, find the centre and radius of the circle. (i) x ^2 + y ^2 + 2x + 4y - 45 = 0

Does each of the following equation represent a circle? If so, find the centre and radius of the circle. (ii) x ^2 + y ^2 - 4x + 5 = 0

A circle passes through the point of intersection of the circles x ^2 + y ^2 + 13x - 3y = 0 and 2x ^2 + 2y ^2 + 4x - 7y - 25 = 0 and also through the point (1, 1). Find its equation.

Find the equation of the tangents to the circle x ^2 + y ^2 - 2x - 4y - 4 = 0 which are perpendicular to the line 3x - 4y - 1 = 0