Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    f(x)=3(2^-x)-1
    The function g is g(x)=\log_2 x
    Find fg(x), giving your answer in its simplest form.

    Okay, the answer is supposed to be \frac{3}{x}-1

    What I've done so far
    f(\log_2 x )=3( 2^\-log_2 x ) -1
    (The log has a minus in front of it but I don't know how to get that to work in Latex)

    =3(2^\log_2 x^-1) -1
    Not sure how to get it in the form needed
    Offline

    17
    ReputationRep:
    (Original post by mintmocha)
    f(x)=3(2^-x)-1
    The function g is g(x)=\log_2 x
    Find fg(x), giving your answer in its simplest form.

    Okay, the answer is supposed to be \frac{3}{x}-1

    What I've done so far


    Not sure how to get it in the form needed
    Note that a^{\log _a k} = k. In your case, a=2 and k=...
    Offline

    2
    ReputationRep:
    2^log_2 (x^-1)=x^-1
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by Farhan.Hanif93)
    Note that a^{\log _a k} = k. In your case, a=2 and k=...
    Ah, thank you!
    I didn't know about this rule.
 
 
 

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
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.