Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

iluvvyyhu

Precalc help please???:( Solving inequalities with one variable? Sign chart? *In exercises 1-6, determine the x values that cause the polynomial function to be (a)zero (b)positive (c)negative.

  • one year ago
  • one year ago

  • This Question is Closed
  1. iluvvyyhu
    Best Response
    You've already chosen the best response.
    Medals 0

    \[f()=(x+2)(x+1)(x-5)\]

    • one year ago
  2. iluvvyyhu
    Best Response
    You've already chosen the best response.
    Medals 0

    sorry it should be f(x)

    • one year ago
  3. malical
    Best Response
    You've already chosen the best response.
    Medals 1

    First you figure out when f(x) = 0, which occurs when (x+2) =0 or (x+1) =0 or (x-5) =0. That is pretty easy, x=-2,-1,5. Your number line is -----(-2)-----(-1)------(5)----- Pick a number left of (-2) say (-5) and input it in as f(-5)= -120 therefore The part left of (-2) is negative. The next number is between (-2) and (-1) and is therefore something like (-1.5). f(-1.5) = something positive because when you put it into (x+2) you get a positive number, and into the other two parts of the equation a negative number returns. (1)(-1)(-1) = 1. Therefore that part is positive. Doing so for the other spaces (-1) to (5) and (5) to infinity results in a negative for (-1) to (5) and a positive for (5) to infinity. Therefore: ---negative--(-2)---positive---(-1)----negative----(5)-----positive----

    • one year ago
  4. iluvvyyhu
    Best Response
    You've already chosen the best response.
    Medals 0

    okay i understand that but im unsure of what to put for the answers, because in the back of the book (answers) their like this, (b) -2<x<-1 or x>5 (c) x<-2 or -1<x<5? but i have no clue how they got that

    • one year ago
  5. malical
    Best Response
    You've already chosen the best response.
    Medals 1

    That's what I get for not fully reading the question. They just want to know when that f(x) is positive, a zero, or negative. You use the sign chart to determine when it is negative and positive. So for (a) you wish to find the zeros which are at (-2), (-1), and (5). (b) however asks for when the equation is positive. It just wants the ranges. So the sign chart says that the equation is positive from (-2) to (-1) or x is greater than (-2) but less than (-1). Therefore, -2<x<-1. You don't use an equals inequality because that would imply that both (-2) and (-1) are positive and we know those to be zeros. The second part of the answer for (b) is the second part that is positive: -5<x and then onto infinity. (c) does the same thing but with negatives instead.

    • one year ago
  6. iluvvyyhu
    Best Response
    You've already chosen the best response.
    Medals 0

    omg thankyou so much i wouldve failed my test tomorrow lol my teacher was no help <333

    • one year ago
    • Attachments:

See more questions >>>

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.