Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

iluvvyyhu

  • 2 years ago

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

  • This Question is Closed
  1. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    \[f(x)=(x-7)(3x+1)(x+4)\]

  2. Brittni0605
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    do you need to simplify?

  3. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    You actually have 2 unknowns here. Is there more to this question?

  4. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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

  5. Brittni0605
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I don't see a chart, ill let @ChmE help you.

  6. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Oh no its a sign chart that you make to solve it with lol but okay(:

  7. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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

  8. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I got 7, -1/3 and -4 ....but the -1/3 doesnt look right to me:/

  9. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Thats correct! So that solves our zero.

  10. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    0<x-7 7<x 0<3x+1 -1<3x -1/3<x -4<x

  11. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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****

  12. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Now what do you think the answer will be for the negative?

  13. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    ummm im a little confused now :(

  14. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I don't know how to make a sign chart. I don't ever remember having to do that.

  15. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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

  16. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Oh okay I got it now(:

  17. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    WAITTTTTTT!!!!!!

  18. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Plug in zero

  19. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    o-o? ok lol

  20. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    0>-7*1*4 negative. OMG. Now I need to rethink some things. Im so sorry. Lets try to make a sign chart.

  21. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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

  22. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1352178252794:dw|

  23. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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

  24. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okay thats easier for me to understand(:

  25. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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.

  26. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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 !!

  27. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Umm yes i think so(: ill practice a little more before i goto sleep lol but thanks a bunch <3

  28. ChmE
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    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.

  29. iluvvyyhu
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Oh wow but alright(: thanks again <3

  30. Not the answer you are looking for?
    Search for more explanations.

    Search OpenStudy
    • Attachments:

Ask your own question

Ask a Question
Find more explanations on OpenStudy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.