Turn on thread page Beta
    • Thread Starter
    Offline

    1
    ReputationRep:
    Hi all!

    Now I'm finding this question a little hard. The question is find the rangeof the function defined by f(x) = (2x-1)/(x-5) with the domain 6<x<8


    I subbed in 6 and 8 into the function and got an answer of 5<f(x)<11. The answer in the back of my book is 0<f(x) < 2/3

    A helping hand would be much appreciated! :-)
    • Community Assistant
    • Very Important Poster
    Offline

    20
    ReputationRep:
    Community Assistant
    Very Important Poster
    I'm pretty sure you're correct.

    Have moved this over to maths.
    Offline

    20
    ReputationRep:
    you don't always get the biggest values of y at the ends of the domain...

    if you have a graphical calculator you can plot the curve to see what happens.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Kvothe the Arcane)
    I'm pretty sure you're correct.

    Have moved this over to maths.
    Thanks for your comment.

    And can I clarify, is the substitution method the easiest way to find the range? And does it work every time?
    • Community Assistant
    • Very Important Poster
    Offline

    20
    ReputationRep:
    Community Assistant
    Very Important Poster
    (Original post by Zarantulas)
    Thanks for your comment.

    And can I clarify, is the substitution method the easiest way to find the range? And does it work every time?
    You need to sketch the graph. The bounds of your domain may not be the local maximum and minimum. Your graph is the same as y=2+\dfrac{9}{x-5} and has asymptotes at x=5 and y=2.

    It looks like:

    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Zarantulas)
    Hi all!

    Now I'm finding this question a little hard. The question is find the rangeof the function defined by f(x) = (2x-1)/(x-5) with the domain 6<x<8


    I subbed in 6 and 8 into the function and got an answer of 5<f(x)<11. The answer in the back of my book is 0<f(x) < 2/3

    A helping hand would be much appreciated! :-)
    Can verify that the answer in the book is wrong. Though coming to your 'easiest way' point, it may not always be the case as such for a curve f(x)=x^2 such that x\in [-2,4] then subbing in these values will not give you the correct range.
    • Thread Starter
    Offline

    1
    ReputationRep:
    (Original post by Kvothe the Arcane)
    You need to sketch the graph. The bounds of your domain may not be the local maximum and minimum. Your graph is the same as y=2+\dfrac{9}{x-5} and has asymptotes at x=5 and y=2.

    It looks like:

    OK thank you! :-)
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 9, 2017
Poll
Do you think parents should charge rent?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.