# Thread: quation of a circle

1. ## quation of a circle

The equation of circle A is (x-4)2+(y-2)2=16 and the equation of circle B is (x+6)2+(y+3)2=9. what is the distance between the centers of these circles?

2. One is centered at (4,2) and the other at (-6,-3).

Use the distance formula and see.

3. Originally Posted by jwein4492
The equation of circle A is (x-4)2+(y-2)2=16 and the equation of circle B is (x+6)2+(y+3)2=9. what is the distance between the centers of these circles?
The general form for a circle is
$(x - h)^2 + (y - k)^2 = r^2$
where the center is (h, k). What can you do with this?

-Dan

4. ## thanks now I have one that is

the equation of circle P is (x-3)2+(y+2)2=34 and equation of circle Q is (x-4)2+(y+5)=52 What is the distance between the centers of these circles?

And Use the distance formula to find the distance between the 2 centers. But I dont understand how.

its the square root of (x2-x) to the second + (y2-y)to the second. HELP!!!

5. Originally Posted by jwein4492
The equation of circle A is (x-4)2+(y-2)2=16 and the equation of circle B is (x+6)2+(y+3)2=9. what is the distance between the centers of these circles?
Originally Posted by topsquark
The general form for a circle is
$(x - h)^2 + (y - k)^2 = r^2$
where the center is (h, k). What can you do with this?

-Dan
The first circle has a center at (4, 2). The second circle has a center at (-6, -3).

The distance between any two points $(x_1, y_1)$ and $(x_2, y_2)$ is
$\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}$

Can you take it from here?

-Dan

6. ## No

I dont understandn the square root stuff.

7. Originally Posted by jwein4492
I dont understandn the square root stuff.
$\sqrt{(-6 - 4)^2 + (-3 - 2)^2}$

It's just a plug'n'chug problem from here. Are you having problems simplifying the answer?

-Dan

8. ## yes

yes on simplifying the answer and showing my work on it?
my teacher is really hard to understand and doesnt explain very well.

9. Originally Posted by jwein4492
yes on simplifying the answer and showing my work on it?
my teacher is really hard to understand and doesnt explain very well.
$\sqrt{125} = \sqrt{25 \cdot 5} = \sqrt{25} \cdot \sqrt{5} = 5 \sqrt{5}$

-Dan

10. ## cool

thanks so much i am sure we will talk again.