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Math Help - quadratctic fomula's

  1. #1
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    quadratctic fomula's

    I entered a new era of erm...unhappiness when it comes to this...Could someone help with these...

    Using the quadratic formula to solve x2 4 = 0 and -4x2 + 4x + 80 = 0

    This keeps getting harder lol I know how to do the simple ones but when they are switched up like that it gets hard...
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  2. #2
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    I entered a new era of erm...unhappiness when it comes to this...Could someone help with these...

    Using the quadratic formula to solve x2 4 = 0 and -4x2 + 4x + 80 = 0

    This keeps getting harder lol I know how to do the simple ones but when they are switched up like that it gets hard...
    x^2 - 4 = 0

    x^2 - (2)^2 = 0

    since a^2 - b^2 = (a+b)(a-b)

    you can write (x+2)(x-2) = 0 and find x.

    for -4x^2+4x+80=0 use the quadratic equation formula.

    For a quadratic equation ax^2+bx+c=0, you can find x as:

    x = \frac{-b \pm \sqrt{b^{2}-4ac}}{2a}

    use a, b, and c from your equation to find x.
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  3. #3
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    Quote Originally Posted by harish21 View Post
    x^2 - 4 = 0

    x^2 - (2)^2 = 0

    since a^2 - b^2 = (a+b)(a-b)

    you can write (x+2)(x-2) = 0 and find x.

    for -4x^2+4x+80=0 use the quadratic equation formula.

    For a quadratic equation ax^2+bx+c=0, you can find x as:

    x = \frac{-b \pm \sqrt{b^{2}-4ac}}{2a}

    use a, b, and c from your equation to find x.
    It seems (x = -5) (x = 10) could be appropiate right?
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  4. #4
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    It seems (x = -5) (x = 10) could be appropiate right?
    Looks like you have not seen that formula before.. What method does your book or your class instructor follow to solve these type of questions?
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  5. #5
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    Quote Originally Posted by harish21 View Post
    Looks like you have not seen that formula before.. What method does your book or your class instructor follow to solve these type of questions?
    Actually it's online, and the lesson has that formula but the answers are a bit different, the one you solved for me was

    x = -2 or x = 2 as an anser for my class, I could tell the difference between your anser in mine, though they looked different I think it's the same either way.
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  6. #6
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    Actually it's online, and the lesson has that formula but the answers are a bit different, the one you solved for me was

    x = -2 or x = 2 as an anser for my class, I could tell the difference between your anser in mine, though they looked different I think it's the same either way.
    (x+2)(x-2)=0 means that x = 2 or x = -2 is your answer..

    I was talking about the second problem.. Are you supposed to use the formula I gave earlier on, or are you supposed to do it by completing the square?
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  7. #7
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    Quote Originally Posted by harish21 View Post
    (x+2)(x-2)=0 means that x = 2 or x = -2 is your answer..

    I was talking about the second problem.. Are you supposed to use the formula I gave earlier on, or are you supposed to do it by completing the square?
    Oh, it says use the quadratic formula but I got the anwser
    x = -5 or x = 10
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  8. #8
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    Oh, it says use the quadratic formula but I got the anwser
    x = -5 or x = 10
    If your question is -4x^2+4x+80=0, then the answer you have gotten is wrong...

    plug in a= -4 , b = 4 and c =80 in the formula given in Post#2 and find x..
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  9. #9
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    Quote Originally Posted by harish21 View Post
    If your question is -4x^2+4x+80=0, then the answer you have gotten is wrong...

    plug in a= -4 , b = 4 and c =80 in the formula given in Post#2 and find x..
    x = 5 or x = -4?
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  10. #10
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    x = 5 or x = -4?
    correct!
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  11. #11
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    Quote Originally Posted by harish21 View Post
    correct!
    lol seriesoulsy? because I guessed lol
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  12. #12
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by tysonrss View Post
    lol seriesoulsy? because I guessed lol
    Well, thats gonna harm you, not me, in the exam..
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