What is the equation of the following graph?

Question

anonymous · Answer

attachment

mathstudent55 · Answer

Equation of a circle with radius r, and center at (h, k).

$(x - h)^2 + (y - k)^2 = r^2$

mathstudent55 · Answer

Start by finding two things:
1. What is the radius of the circle?
2. What are the coordinates of the center of the circle?

mathstudent55 · Answer

@biddyB 
Are you there?

anonymous · Answer

Sorry I was actually wrong! mathstudent55 is right. Sorry for the confusion!

anonymous · Answer

Ok, whew, I was really confused for a second. Thats ok, I get it now, thanks

anonymous · Answer

How do I find the radius?

mathstudent55 · Answer

First, find the center.

anonymous · Answer

0?

mathstudent55 · Answer

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mathstudent55 · Answer

I think you got the right idea, but the center is actually (0, 0) since it's a point. It needs to have an x-coordinate and a y-coordinate.

mathstudent55 · Answer

Now that you know where the center is, the radius is the distance from the center point to any point on the circle.

mathstudent55 · Answer

It's easier if you measure along a horizontal or a vertical line.

mathstudent55 · Answer

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anonymous · Answer

3?

mathstudent55 · Answer

Correct.
The radius is 3. That means r = 3
The center of the circle is (0, 0). That means h = 0, and k = 0.
Now we use these values in the equation above.

mathstudent55 · Answer

$(x - h)^2 + (y - k)^2 = r^2$

$(x - 0)^2 + (y - 0)^2 = 3^2$

You see the substitutions of 0 for h, 0 for k, and 3 for r?

mathstudent55 · Answer

Now we just simplify to:

$\large x^2 + y^2 = 9$

That is the answer.