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anonymous

  • one year ago

please help with this problem 3x^3+4x^2=27x+36

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  1. misty1212
    • one year ago
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    HI!!

  2. misty1212
    • one year ago
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    you have a cubic equation to solve?

  3. anonymous
    • one year ago
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    yes can you please explain all the steps for me

  4. misty1212
    • one year ago
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    there is a formula for solving cubes, but it is almost incomprehensible start with \[3x^3+4x^2-27x-36=0\] and then make an educated guess , which is really all you ca ndo

  5. misty1212
    • one year ago
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    i guess 3, since 1 and -1 do not work shall we try it?

  6. anonymous
    • one year ago
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    ok

  7. misty1212
    • one year ago
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    i;ll be damned, it works!

  8. misty1212
    • one year ago
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    got it in the first try so this is \[(x-3)(\text{ some quadratic})\]which you can find using synthetic division or long division (ugh) or thinking (or cheating)

  9. misty1212
    • one year ago
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    i can't write synthetic division here, but i can cheat or think you pick

  10. anonymous
    • one year ago
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    idk

  11. misty1212
    • one year ago
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    http://www.wolframalpha.com/input/?i=3x%5E3%2B4x%5E2-27x-36%3D0

  12. anonymous
    • one year ago
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    tnx

  13. JohnN.
    • one year ago
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    Let's solve your equation step-by-step. 3x3+4x2=27x+36 Step 1: Subtract 27x+36 from both sides. 3x3+4x2−(27x+36)=27x+36−(27x+36) 3x3+4x2−27x−36=0 Step 2: Factor left side of equation. (x+3)(x−3)(3x+4)=0 Step 3: Set factors equal to 0. x+3=0 or x−3=0 or 3x+4=0 x=−3 or x=3 or x=−43 Answer: x=−3 or x=3 or x=−43

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