The equation of a circle in the xy-plane is shown here:
$$ x^2 + y^2 + 6x – 4y = –9 $$
What is the radius of the circle?

Question

Uniteasy Admin · Accepted Answer

Convert the equation to the standard circle equation
$$ (x – h)^2 + (y – k)^2 = r^2$$
in which r is the radius of the circle.
$$ x^2+y^2+6x-4y=-9$$
$$x^2+6x+9+y^2-4y+2=-9+9+4$$
$$(x+3)^2+(y-2)^2=2^2$$
Therefore the radius of the circle is 2
B is correct choice

Multiple Choice Question (MCQ)

Answer