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anonymous

  • 5 years ago

Find the zeros of the function x^2 - x-4

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  1. shadowfiend
    • 5 years ago
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    Do you know how to factor this equation?

  2. anonymous
    • 5 years ago
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    Yes but my problem is, is that I can't think of anything that added toger is 1 and multi to get 4

  3. shadowfiend
    • 5 years ago
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    Hm. Fair enough. So there are a couple of ways to approach this. Do you know the quadratic formula?

  4. anonymous
    • 5 years ago
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    yes -2 +- \[-b +_\sqrt{b^2 - 4ac} \over 2a\]

  5. shadowfiend
    • 5 years ago
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    Right. Do you know what a, b, and c are in your equation?

  6. anonymous
    • 5 years ago
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    yes a is 1x^2 b is 1x and c is 4

  7. shadowfiend
    • 5 years ago
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    Close, a, b, and c are the coefficients -- so a is 1, b is -1, and c is -4. Remember that a minus sign is part of the coefficient :) Can you plug those in?

  8. anonymous
    • 5 years ago
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    yeah I get \[1 \pm \sqrt{15} \over 2\]

  9. shadowfiend
    • 5 years ago
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    Right-o. And there are your two zeros.

  10. anonymous
    • 5 years ago
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    what are the two zeros?

  11. shadowfiend
    • 5 years ago
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    The quadratic equation describes two results: \[x = \frac{1 + \sqrt{15}}{2}\] and \[x = \frac{1 - \sqrt{15}}{2}\] Those are the two zeros of the equation.

  12. anonymous
    • 5 years ago
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    oh, ok thanks alot

  13. shadowfiend
    • 5 years ago
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    No problem, glad to help :)

  14. anonymous
    • 5 years ago
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    wouldn't this be 17 instead of 15?

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