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Math Help - solution of the quadratic equation

  1. #1
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    solution of the quadratic equation

    Question

    x^2-4=0

    Attempt

    Using the Formula I got 4

    Is my answer correct?
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  2. #2
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    Quote Originally Posted by mj.alawami View Post
    [SIZE=4]Question

    x^2-4=0
    From what you learned about factoring quadratics and special factoring formulas, you know that the above can be restated as:

    . . . . . (x\, -\, 2)(x\, +\, 2)\,=\, 0

    What result do you get when you solve the factors?

    Quote Originally Posted by mj.alawami View Post
    Using the Formula I got 4

    Is my answer correct?
    The Quadratic Formula gives a result (using a = 1, b = 0, and c = -4) that agrees with the "by factoring" result. What formula did you use?

    Note: The answer to any "solving" problem can be checked by plugging it back into the original exercise. In your case:

    . . . . . x^2\, -\, 4\, =\, (4)^2\, -\, 4\, =\, 16\, -\, 4\, =\, 12\, \neq \, 0

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  3. #3
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    Quote Originally Posted by stapel View Post
    From what you learned about factoring quadratics and special factoring formulas, you know that the above can be restated as:

    . . . . . (x\, -\, 2)(x\, +\, 2)\,=\, 0

    What result do you get when you solve the factors?


    The Quadratic Formula gives a result (using a = 1, b = 0, and c = -4) that agrees with the "by factoring" result. What formula did you use?

    Note: The answer to any "solving" problem can be checked by plugging it back into the original exercise. In your case:

    . . . . . x^2\, -\, 4\, =\, (4)^2\, -\, 4\, =\, 16\, -\, 4\, =\, 12\, \neq \, 0


    I have done
     x^2 -4 +0 =0
    Then I Used the Quadratic Formula and Got 4
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  4. #4
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    Quote Originally Posted by mj.alawami View Post

    I have done
     x^2 -4 +0 =0
    Then I Used the Quadratic Formula and Got 4

    So to Finalize the answer is -2

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  5. #5
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by mj.alawami View Post
    So to Finalize the answer is -2
    no

    Quote Originally Posted by mj.alawami View Post

    I have done
     x^2 -4 +0 =0
    Then I Used the Quadratic Formula and Got 4
    and the purpose of adding zero to the left side was...?

    -4 is your constant term, that is the "c" in your formula. thus you have a = 1, b = 0 and c = -4

    applying the quadratic formula, we have

    x = \frac {-0 \pm \sqrt{0^2 - 4(1)(-4)}}{2(1)} = \frac {\pm \sqrt{16}}{2} = \pm \frac 42 = \pm 2


    for problems like these, the quadratic formula is overkill. either do what stapel did, or just add 4 to both sides and then square root both sides (and remember that the right side will have a +/- with it, since there are two square roots to a number)
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