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burhan101

  • 2 years ago

x intercept for this function

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  1. burhan101
    • 2 years ago
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    \[\huge y=x^3-9x^2+15x+4\]

  2. burhan101
    • 2 years ago
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    this is unfactorable?

  3. timo86m
    • 2 years ago
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    oh no wait nevermind

  4. SmoothMath
    • 2 years ago
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    Any particular method they want you to use? Do they specify factoring?

  5. burhan101
    • 2 years ago
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    No but isnt that the only way?

  6. SmoothMath
    • 2 years ago
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    Graphing is the easiest.

  7. SmoothMath
    • 2 years ago
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    Graph that bad boy. Look for where it crosses the x axis. Doneso.

  8. burhan101
    • 2 years ago
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    no i have to use an algebraic method

  9. burhan101
    • 2 years ago
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    because like say on an exam, i cant graph that

  10. Mertsj
    • 2 years ago
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    Possible rational roots are :

  11. SmoothMath
    • 2 years ago
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    Okay then your best best is to use the rational root theorem to list possible rational roots. Then check each one to see if it is a valid root.

  12. Mertsj
    • 2 years ago
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    \[\pm1,\pm4,\pm2\]

  13. Mertsj
    • 2 years ago
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    Use synthetic division to see if any of those are actual roots.

  14. SmoothMath
    • 2 years ago
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    Mertsj is correct. The way he got those possible roots is: A: Make a list of factors for the last number (In this case, it's 4) B: Make a list of factors for the first coefficient (In this case, it's 1) Possible rational roots must be of the form \(\huge \frac{\text{things in the first list}}{\text{things in the second list}}\)

  15. Mertsj
    • 2 years ago
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    It is not factorable.

  16. Mertsj
    • 2 years ago
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    So the best approach would be to find where y changes sign. Then you would know there is a root between those two values and you could hone in on it by trial and error. Of if you know calculus, you could use the derivative. What class is this for?

  17. burhan101
    • 2 years ago
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    @Mertsj calculus !

  18. oldrin.bataku
    • 2 years ago
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    they want you to bruteforce using newton's more than likely

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