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iluvvyyhu Group Title

Can someone help me with this? Precalc solving inequalities with one variable? The 3x is throwing me off

  • 2 years ago
  • 2 years ago

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  1. iluvvyyhu Group Title
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    \[f(x)=(x-7)(3x+1)(x+4)\]

    • 2 years ago
  2. Brittni0605 Group Title
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    do you need to simplify?

    • 2 years ago
  3. ChmE Group Title
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    You actually have 2 unknowns here. Is there more to this question?

    • 2 years ago
  4. iluvvyyhu Group Title
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    No, you use a sign chart. @Brittni0605 And yes sorry it says *In the exercises 1-6 determine the x values that cause the polynomial functions to be (a)zero (b) positive and (c)negative @ChmE

    • 2 years ago
  5. Brittni0605 Group Title
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    I don't see a chart, ill let @ChmE help you.

    • 2 years ago
  6. iluvvyyhu Group Title
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    Oh no its a sign chart that you make to solve it with lol but okay(:

    • 2 years ago
  7. ChmE Group Title
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    so we set it equal to zero, then less than for negative, then greater than for positive. Ok. Let's start with setting it equal to zero. Do not distribute, leave the equation as is. Go to each ( ) and think what will x need to be to make this zero. Only one needs to be zero for the whole thing to be zero. There should be 3 answers. I'll give you a sec. Let me know if you didn't understand what I just said

    • 2 years ago
  8. iluvvyyhu Group Title
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    I got 7, -1/3 and -4 ....but the -1/3 doesnt look right to me:/

    • 2 years ago
  9. ChmE Group Title
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    Thats correct! So that solves our zero.

    • 2 years ago
  10. ChmE Group Title
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    0<x-7 7<x 0<3x+1 -1<3x -1/3<x -4<x

    • 2 years ago
  11. ChmE Group Title
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    But here is where it is tricky. Say we use the number 0 which satisfies the first but not the last two. Lets see if we get a positive number. 0<(0-7)(3(0)+1)(0+4) 0<-7*1*4 0<-28 no. So the answer for 0<.... is x<-4 because that is the lowest. ***I missed typed above this is for the positive****

    • 2 years ago
  12. ChmE Group Title
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    Now what do you think the answer will be for the negative?

    • 2 years ago
  13. iluvvyyhu Group Title
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    ummm im a little confused now :(

    • 2 years ago
  14. ChmE Group Title
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    I don't know how to make a sign chart. I don't ever remember having to do that.

    • 2 years ago
  15. iluvvyyhu Group Title
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    Umm well im not sure i think i kinda get it a little better? Im sorry this is taking long btw, just my teacher never helped me lol

    • 2 years ago
  16. iluvvyyhu Group Title
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    Oh okay I got it now(:

    • 2 years ago
  17. ChmE Group Title
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    WAITTTTTTT!!!!!!

    • 2 years ago
  18. ChmE Group Title
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    Plug in zero

    • 2 years ago
  19. iluvvyyhu Group Title
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    o-o? ok lol

    • 2 years ago
  20. ChmE Group Title
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    0>-7*1*4 negative. OMG. Now I need to rethink some things. Im so sorry. Lets try to make a sign chart.

    • 2 years ago
  21. iluvvyyhu Group Title
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    lol okay|dw:1352178275962:dw| would i put the 1/3 on it though? i dont know lol Its bothering me since its a fraction lol

    • 2 years ago
  22. ChmE Group Title
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    |dw:1352178252794:dw|

    • 2 years ago
  23. ChmE Group Title
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    so when it is negative is x<-4, -1/3<x<7 so when it is positive it is -4<x<-1/3, x>7

    • 2 years ago
  24. iluvvyyhu Group Title
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    okay thats easier for me to understand(:

    • 2 years ago
  25. ChmE Group Title
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    How to solve problems like this. Set equal to zero. Solve each term for the zeros. Put those points on a number line. Pick easy numbers between those points. Test to see if it is positive or negative. Follow the number line like a map to get the solutions for neg and pos.

    • 2 years ago
  26. ChmE Group Title
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    Sorry for leading you estray but sometimes working through a problem and finding mistakes helps us understand a little more about the correct way in terms of what is not right. I think a sign graph is very helpful, I'd continue to use that. Do you think you could do a problem like this by yourself now? Thanks for refreshing me as well. It took a while but we got it !!

    • 2 years ago
  27. iluvvyyhu Group Title
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    Umm yes i think so(: ill practice a little more before i goto sleep lol but thanks a bunch <3

    • 2 years ago
  28. ChmE Group Title
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    I'm in differential equations right now which is Calc 4, and I almost got this question wrong, humbling. Good luck and check your work if you have time, it's very beneficial.

    • 2 years ago
  29. iluvvyyhu Group Title
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    Oh wow but alright(: thanks again <3

    • 2 years ago
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