1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the Domain of l/g Without first calculating (l/g)(x)

  1. Jul 1, 2015 #1
    1. The problem statement, all variables and given/known data
    Write down Dl/g without first calculating (l/g)(x)

    2. Relevant equations
    g(x)=-(1/2)x-3
    l(x)=√(2-x)-3

    3. The attempt at a solution
    g(x)=-(1/2)x-3 Dg = {x∈ℝ}
    l(x)=√(2-x)-3 Dl = {x∈ℝ:x≤2}
    Dg/l = {x∈ℝ:x≤2}
     
  2. jcsd
  3. Jul 1, 2015 #2

    Fredrik

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The problem asked for the domain of l/g.

    Why would the domain of g/l be the same as the domain of l?
     
  4. Jul 1, 2015 #3

    Mentallic

    User Avatar
    Homework Helper

    As you guessed, you needed to find the intersection of both domains, but you're also forgetting one thing - there's a problem with division.
     
  5. Jul 1, 2015 #4

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Not quite.

    What does your textbook or notes say about the domain of the quotient of two functions?
     
  6. Jul 1, 2015 #5
    Denominator can't be 0

    g(x)=-(1/2)x-3 Dg = {x∈ℝ}
    l(x)=√(2-x)-3 Dl = {x∈ℝ:x≤2}
    l(x)≠0
    Dg/l = {x∈ℝ:x≤2 and x≠-5}
     
  7. Jul 1, 2015 #6

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Looks good.
     
  8. Jul 1, 2015 #7
    Thank you everyone.
     
  9. Jul 1, 2015 #8

    Mentallic

    User Avatar
    Homework Helper

    Your thread title and opening sentence made it a little confusing, but you understand the process so that's all that matters.

     
  10. Jul 1, 2015 #9
    Thank you Mentallic,
    what would a better title be for future use?

    Thank you for the help.
    Jaco
     
  11. Jul 1, 2015 #10

    Mentallic

    User Avatar
    Homework Helper

    It wasn't so much the title as it was the confusion of the actual question. You mentioned calculating Dl/g but then went on to find Dg/l.

    But regardless, a title such as "Domain of function" would suffice.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What is the Domain of l/g Without first calculating (l/g)(x)
  1. Domain of f o g (Replies: 10)

Loading...