Question

1. The equation of a circle is x^2 + y^2 + 6x - 4y + 4 = 0. What are the center and the radius of the circle? Show ALLLLLL your work

Answer 1

Answer:

(2, -3) and r = 3.

Step-by-step explanation:

you can also plug this equation in desmos but I guess it's good to know how to do it also:

The equation of a circle is (x-h)^2 + (y-k)^2 = r^2

Now in order to make a perfect square on both sides, we need to do this:

First add 9 to both sides:

x^2 + 6x + 9 + y^2 -4y +4 = 9.

I purposely shifted it to show the perfect square created when you add 9 to both sides. Factor:

(x+3)^2 + y^2 - 4y + 4 = 9.

now the second bolded part is allso a perfect square. Factor:

(x+3)^2 + (y-2)^2 = 9

Based on the equation of a circle, the center must be at (2, -3) and the radius is the square root of 9 which is 3.

:)