Question

What is the radius of a circle whose equation ?????

Answer 1

$r = \sqrt{ L^{2} + K^{2} -C} = \sqrt{ (-4)^{2} + (3)^{2} - 21 } = \sqrt{4} = 2$

where L is negative half the coefficient of x and K is negative half the coefficient of y and c is the term free of x and y