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Thread: Solve 2^2-5X+2=0

  1. #1
    Newbie danthegreat's Avatar
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    Solve 2^2-5X+2=0

    Solve 2^2-5X+2=0

    I forgot how to do this. I get x=4,1 but that's wrong. I thought you multiply 2*2 and then you know that you need a factor of 4 that adds up to 5 which are 4 and 1.

    Then what?
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  2. #2
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    Re: Solve 2^2-5X+2=0

    $\displaystyle is\ it\ 2^2 - 5x + 2 = 0 , if\ it\ is\, then\ 4 - 5x + 2 = 0 \Rightarrow -5x + 6 = 0 \Rightarrow -5x = -6 \Rightarrow x = \frac{6}{5}.$
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  3. #3
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    Re: Solve 2^2-5X+2=0

    Quote Originally Posted by danthegreat View Post
    Solve 2^2-5X+2=0

    I forgot how to do this. I get x=4,1 but that's wrong. I thought you multiply 2*2 and then you know that you need a factor of 4 that adds up to 5 which are 4 and 1.

    Then what?
    did you really mean ...

    $\displaystyle 2x^2 - 5x + 2 = 0$

    if so ...

    $\displaystyle (2x - 1)(x - 2) = 0$

    $\displaystyle x = \frac{1}{2}$ , $\displaystyle x = 2$
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  4. #4
    Newbie danthegreat's Avatar
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    Re: Solve 2^2-5X+2=0

    Quote Originally Posted by skeeter View Post
    did you really mean ...

    $\displaystyle 2x^2 - 5x + 2 = 0$

    if so ...

    $\displaystyle (2x - 1)(x - 2) = 0$

    $\displaystyle x = \frac{1}{2}$ , $\displaystyle x = 2$
    where did you get 1 and 2? (bolded)
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    Re: Solve 2^2-5X+2=0

    Quote Originally Posted by danthegreat View Post
    where did you get 1 and 2? (bolded)
    We know that if this equation is factorable, that we will get the following form (Ax $\displaystyle \pm$ B)(Cx$\displaystyle \pm$D) = 0

    He first took $\displaystyle 2x^2$ and factored it. 2 is a prime number so, it's factor's are just 2 and 1, so we know what A and C should be.

    (2x $\displaystyle \pm$ B)(1x$\displaystyle \pm$D) = 0

    Using FOIL, we know that the last two terms will be multiplied together to come up with a constant. In our case, the constant is 2. Again it is a prime. So B and D are going to be a combination of 1 and 2. Since the last constant in the original equation is a positive number, we know that when multiplied together using FOIL B and D will be both positive or both negative.

    Hope that helps some
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  6. #6
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    Re: Solve 2^2-5X+2=0

    Quote Originally Posted by danthegreat View Post
    where did you get 1 and 2? (bolded)
    go to the link and learn ...

    Solving Quadratic Equations: Solving by Factoring
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