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Thread: basic Solve for x and y problem i'm stuck on.

  1. #1
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    basic Solve for x and y problem i'm stuck on.

    Hey all,


    I’ve got ‘solve for X and Y’ issues.


    ….here’s three examples:


    133 = 350 - ( (x - 95)^2 + (y - 85)^2 ) * 2


    47 = 350 - ( (x - 160)^2 + (y - 85)^2 ) * 2


    172 = 350 - ( (x - 128)^2 + (y - 160)^2 ) * 2


    I’m building a little “color-selector” website for converting red, green, blue color codes. There are a lot of little sites that do it. I just wanted to build my own for fun. I’ll post the link when finished! My Algebra is all but lost, so any help/Explanation would be much appreciated!


    Thanks in advance!
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  2. #2
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    Re: basic Solve for x and y problem i'm stuck on.

    133 = 350 - √[(x - 95)^2 + (y - 85)^2] * 2

    Simplifies to:
    √[(x - 95)^2 + (y - 85)^2] = (350 - 133) / 2

    Square both sides:
    (x - 95)^2 + (y - 85)^2 = [(350 - 133) / 2]^2

    Best you can do...any value of x will yield a y value.
    Since you have 2 unknowns, you need 2 equations.
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  3. #3
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    Re: basic Solve for x and y problem i'm stuck on.

    Quote Originally Posted by DenisB View Post
    133 = 350 - √[(x - 95)^2 + (y - 85)^2] * 2

    Simplifies to:
    √[(x - 95)^2 + (y - 85)^2] = (350 - 133) / 2

    Square both sides:
    (x - 95)^2 + (y - 85)^2 = [(350 - 133) / 2]^2

    Best you can do...any value of x will yield a y value.
    Since you have 2 unknowns, you need 2 equations.
    Thanks DenisB,

    I forgot to mention that x and y are both the same for all three equations...

    133 = 350 - √( (x - 95)^2 + (y - 85)^2 ) * 2


    47 = 350 - √( (x - 160)^2 + (y - 85)^2 ) * 2


    172 = 350 - √( (x - 128)^2 + (y - 160)^2 ) * 2

    ... Is that enough to solve for both? or do i still need x or y?

    Thanks!
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  4. #4
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    Re: basic Solve for x and y problem i'm stuck on.

    Simplify two of the equations like dennisb did, then solve for x and y like you would a normal system. I would use the first two equations because they both have the both have the (y-85)^2 term.

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  5. #5
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    Re: basic Solve for x and y problem i'm stuck on.

    Quote Originally Posted by lastplace199 View Post
    Simplify two of the equations like dennisb did, then solve for x and y like you would a normal system. I would use the first two equations because they both have the both have the (y-85)^2 term.

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    So it sounds like I have all I need to solve...

    ....however it's the "solve for x and y like you would a normal system" bit that I'm stuck on... understand it's basic Algebra, but I'm just embarrassing stuck trying to work it out...:-/

    Any help/ references would be great! dennisB got me out to a good start, but don't know how to work it from there with 2 equations to solve for both...
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  6. #6
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    Re: basic Solve for x and y problem i'm stuck on.

    http://www.wtamu.edu/academic/anns/m...t19_systwo.htm


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  7. #7
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    Re: basic Solve for x and y problem i'm stuck on.

    Solving using 1st 2 equations results in x = 83/2 and y = 85 - 9*sqrt(110)

    However, substituting above in 3rd equation gives -30.4 instead of 172.
    So 3rd equation is wrong.

    And as Lastplace199 told you, you need to learn the solving process,
    and that's impossible to teach from here.
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