A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

Solve lim X2-x+12 x -> 3 --------- X-3

  • This Question is Closed
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Hint: \(x^2-x+12=(x-3)(x-\mathbin{?})\)

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

    I tried to factorize and couldnt find second term and tried with synthetic division and I couldnt

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

    what happened when you plugged in 3? if you got something/0 where the something was zero then you have more work if you have something that was not 0 then your work is done and you can say the limit does not exist

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

    so what is 3^2-3+12?

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

    Answer must be -1

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

    \[(x-3)(x-\mathbin{\color{red}{?}})=x^2-3x-\mathbin{\color{red}?}x+3\mathbin{\color{red}?}\] This is supposed to be equivalent to \(x^2-x+12\). This means \[\begin{cases} x^2=x^2&\text{okay}\\ -x=-3x-\mathbin{\color{red}?}x&\text{you can solve this eq. for }\mathbin{\color{red}?}...\\ 12=3\mathbin{\color{red}?}&\text{or this one}\\ \end{cases}\]

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

    @Gloria63 how do you get -1?

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

    if you had: \[\lim_{x \rightarrow 3}\frac{x^2-7x+12}{x-3} \text{ I would be able \to see how you got -1 } \\ x^2-7x+12=(x-3)(x-4) \\ \lim_{x \rightarrow 3}\frac{(x-3)(x-4)}{x-3}=\lim_{x \rightarrow 3}(x-4)=3-4=-1\]

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

    but you had \[x^2-x+12\]

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

    \[\lim_{x \rightarrow 3}\frac{f(x)}{g(x)} \\ \\ \text{ If } f(3) \text{ and } g(3)=0 \text{ then you have more work } \\ \text{ If } f(3) \neq 0 \text{ and } g(3)=0 \text{ then the limit does \not exist }\]

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

    Teacher just said this is the correct answer -1

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

    the limit does not exist \[\lim_{x \rightarrow 3}\frac{x^2-x+12}{x-3} \\ \text{ since } 3^2-3+12=18 \text{ and } 3-3=0 \\ \text{ so we have } \frac{18}{0 } \\ \text{ the limit does not exist } \\ \text{ there must be a type-o if your teacher says it is -1 }\]

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

    http://www.wolframalpha.com/input/?i=limit%28%28x%5E2-x%2B12%29%2F%28x-3%29%2Cx%3D3%29 here is another source if you don't believe me

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

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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.