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Math Help - quation of a circle

  1. #1
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    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?
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  2. #2
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    One is centered at (4,2) and the other at (-6,-3).

    Use the distance formula and see.
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  3. #3
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    Quote Originally Posted by jwein4492 View Post
    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
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  4. #4
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    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!!!
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  5. #5
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by jwein4492 View Post
    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?
    Quote Originally Posted by topsquark View Post
    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
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  6. #6
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    No

    I dont understandn the square root stuff.
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  7. #7
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by jwein4492 View Post
    I dont understandn the square root stuff.
    What are you confused about?
    \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
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  8. #8
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    yes

    yes on simplifying the answer and showing my work on it?
    my teacher is really hard to understand and doesnt explain very well.
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  9. #9
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by jwein4492 View Post
    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
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  10. #10
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    Cool cool

    thanks so much i am sure we will talk again.
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