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Math Help - How would you solve 7x^2-10x=4x^3-9?

  1. #1
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    How would you solve 7x^2-10x=4x^3-9?

    7x2-10x=4x3-9
    x=?
    Last edited by EJdive43; August 13th 2012 at 01:28 PM.
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    Re: How would you solve 7x^2-10x=4x^3-9?

    Quote Originally Posted by EJdive43 View Post
    7x2-10x=4x3-9
    x=?
    4x^3-7x^2+10x-9=0
    There is no 'nice' answer.
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    Re: How would you solve 7x^2-10x=4x^3-9?

    But I got x= 7/4,9, and 1
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    Re: How would you solve 7x^2-10x=4x^3-9?

    Quote Originally Posted by EJdive43 View Post
    But I got x= 7/4,9, and 1
    None of that is correct.
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    Re: How would you solve 7x^2-10x=4x^3-9?

    1)I thought you bring everything to one side: -4x^3+7x^2-10x-9=0
    2) then you factor: x^2(-4x+7)-10x+9=0
    3) then set everything to zero: (-4x+7)=0 x^2-10x+9=0
    4) then solve: X=7/4. X=9 x=1
    Is that not right? What did I do wrong? >_<
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    Re: How would you solve 7x^2-10x=4x^3-9?

    Quote Originally Posted by EJdive43 View Post
    1)I thought you bring everything to one side: -4x^3+7x^2-10x-9=0
    2) then you factor: x^2(-4x+7)-10x+9=0
    3) then set everything to zero: (-4x+7)=0 x^2-10x+9=0
    4) then solve: X=7/4. X=9 x=1
    Is that not right? What did I do wrong? >_<
    Here is the solution.
    Attached Thumbnails Attached Thumbnails How would you solve 7x^2-10x=4x^3-9?-untitled.gif  
    Last edited by Plato; August 13th 2012 at 02:10 PM.
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    Re: How would you solve 7x^2-10x=4x^3-9?

    Quote Originally Posted by EJdive43 View Post
    1)I thought you bring everything to one side: -4x^3+7x^2-10x-9=0
    2) then you factor: x^2(-4x+7)-10x+9=0
    3) then set everything to zero: (-4x+7)=0 x^2-10x+9=0 this step is incorrect ... one sets factors equal to zero, not terms.
    4) then solve: X=7/4. X=9 x=1
    Is that not right? What did I do wrong? >_<
    ...
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  8. #8
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    Re: How would you solve 7x^2-10x=4x^3-9?

    If your really believe that 7- 10= 4- 9, then your first mistake was not paying attention in arithmetic!
    Last edited by HallsofIvy; August 13th 2012 at 04:38 PM.
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