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Thread: Solving equations

  1. #1
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    Solving equations

    Please help me to solve these equations:

    3x - 4 = x + 5


    X x 3X = x2 + 4
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  2. #2
    Newbie joserizal's Avatar
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    Quote Originally Posted by Shandy View Post
    Please help me to solve these equations:

    3x - 4 = x + 5
    $\displaystyle 3x-x = 5+4$

    $\displaystyle 2x=9$

    $\displaystyle x=\frac{9}{2}$

    lets check it.

    $\displaystyle 3 * \frac{9}{2} - 4 = \frac{9}{2} + 5$

    $\displaystyle \frac{27}{2} - \frac{8}{2} = \frac{9}{2} +\frac{10}{2}$

    $\displaystyle \frac{19}{2}= \frac{19}{2}$


    X x 3X = x2 + 4
    i assume that this is your equation. $\displaystyle x*3x = x^2 +4$

    $\displaystyle 3x^2= x^2 +4$

    $\displaystyle 3x^2-x^2 = 4$

    $\displaystyle 2x^2=4$

    $\displaystyle \sqrt{2x^2}=\sqrt{4}$

    $\displaystyle x\sqrt{2}=2$

    $\displaystyle x=\frac{2}{\sqrt{2}}$

    $\displaystyle
    x=\frac{2}{\sqrt{2}}*\frac{\sqrt{2}}{\sqrt{2}}
    $

    $\displaystyle x=\frac{2\sqrt{2}}{2}$

    $\displaystyle x=\sqrt{2}$

    $\displaystyle \sqrt{2}*\sqrt{2}^2= \sqrt{2}^2 + 4$

    $\displaystyle 4+2= 2+4$

    $\displaystyle 6=6$
    Last edited by joserizal; Feb 3rd 2009 at 12:10 AM.
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  3. #3
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    Thank you very much, but I made a little mistake on the second one. It was supposed to be:

    X * 3X = -X^2 + 4

    Could you please help me with that one!

    Thanks again!
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  4. #4
    Newbie joserizal's Avatar
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    Quote Originally Posted by Shandy View Post
    Thank you very much, but I made a little mistake on the second one. It was supposed to be:

    X * 3X = -X^2 + 4

    Could you please help me with that one!

    Thanks again!
    $\displaystyle X * 3X = -X^2 + 4$

    $\displaystyle 3x^2= -x^2 +4$

    $\displaystyle 3x^2+x^2=4$

    $\displaystyle 4x^2=4$

    $\displaystyle x^2=\frac{4}{4}$

    $\displaystyle \sqrt{x}^2=1$

    $\displaystyle
    x=1
    $

    let's check it.

    $\displaystyle 1 * 3 = -1 +4$

    $\displaystyle 3=3$
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