Turn on thread page Beta
    • Thread Starter
    Offline

    15
    ReputationRep:
    Is there a way to get an exact answer to:

    0.75n + 1 = (4/3)n ?

    Thanks.
    Offline

    12
    ReputationRep:
    (Original post by Simba)
    Is there a way to get an exact answer to:

    0.75n + 1 = (4/3)n ?

    Thanks.
    I cant find any solutions to that, have you typed it up right?
    (or it could be way past my understanding of maths )
    • Thread Starter
    Offline

    15
    ReputationRep:
    Well, there appears to be a solution around 1.675... but I would like it as an exact fraction, and I'm not sure how to work it out as an exact fraction ...

    Thanks anyway ...

    ~~Simba
    Offline

    0
    ReputationRep:
    (Original post by Simba)
    Is there a way to get an exact answer to:

    0.75n + 1 = (4/3)n ?

    Thanks.
    You can re-write the above equation in the form:

    X + 1 = X^-1

    where X = 0.75^n. This can be rearranged into:

    X^2 + X - 1 = 0

    which is a quadratic equation.

    You can do the rest.
    • Thread Starter
    Offline

    15
    ReputationRep:
    Thanks !

    I'm left with 0.75n = (-1 ± √5)/2

    So nlog0.75 = log[(-1 + √5)/2]

    n = log[(-1 + √5)/2]/log 0.75

    So how do I get 'n' as an exact fraction *Rubs head*?
    Offline

    0
    ReputationRep:
    I think n is irrational.
    Offline

    0
    ReputationRep:
    You don't, you already have the answer in exact form.

    The answer may very well be irrational anyway.
    • Thread Starter
    Offline

    15
    ReputationRep:
    Ok, thank you ... I was expecting the answer to be rational; otherwise (4/3)n will be irrational... but, never mind ...

    Thanks,

    ~~Simba
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: December 3, 2005

University open days

  • University of East Anglia
    UEA Mini Open Day Undergraduate
    Fri, 4 Jan '19
  • University of Lincoln
    Mini Open Day at the Brayford Campus Undergraduate
    Mon, 7 Jan '19
  • Bournemouth University
    Undergraduate Mini Open Day Undergraduate
    Wed, 9 Jan '19
Poll
Did you get less than your required grades and still get into university?
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

Equations

Best calculators for A level Maths

Tips on which model to get

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.