Turn on thread page Beta
    • Thread Starter
    Offline

    10
    ReputationRep:
    Given that 64^y = 2^3y-1, find the value of y. I don't even know where to begin.
    • Political Ambassador
    Offline

    17
    ReputationRep:
    Political Ambassador
    Use logs I think
    Offline

    16
    ReputationRep:
    Look up "logarithms".
    • Political Ambassador
    Offline

    17
    ReputationRep:
    Political Ambassador
    so Logy64=Log(3y-1)2
    Offline

    1
    ReputationRep:
    64 = 8^2
    8 = 2^3

    therefore 2^6 = 64

    2^6y = 2^3y-1

    6y = 3y-1 (base the same)

    rearrange to get y (I presume -1 is part of the power)
    Offline

    1
    ReputationRep:
    (Original post by Texxers)
    so Logy64=Log(3y-1)2
    logs is in C2, not C1
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Chef289)
    64 = 8^2
    8 = 2^3

    therefore 2^6 = 64

    2^6y = 2^3y-1

    6y = 3y-1 (base the same)

    rearrange to get y (I presume -1 is part of the power)
    I wish I could find more similar problems in my C1 textbook. How did you go about doing it? I understand what you did, but I don't get why.
    Online

    18
    ReputationRep:
    Firstly change them all to the same base Once you have that you can equal the powers
    Offline

    3
    ReputationRep:
    Laws of indices: (2^3)^y is the same as 2^3y

    basically keep changing them until its the same base, and then you'll have something where both sides are equivalent and you can equal to powers
    Offline

    1
    ReputationRep:
    (Original post by Student1914)
    I wish I could find more similar problems in my C1 textbook. How did you go about doing it? I understand what you did, but I don't get why.
    Here's a website that tells you the basics. Law of Indices.

    http://mathematics.laerd.com/maths/indices-intro.php
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by nisha.sri)
    Firstly change them all to the same base Once you have that you can equal the powers
    (Original post by potassiumnitrate)
    Laws of indices: (2^3)^y is the same as 2^3y

    basically keep changing them until its the same base, and then you'll have something where both sides are equivalent and you can equal to powers
    (Original post by Chef289)
    Here's a website that tells you the basics. Law of Indices.

    http://mathematics.laerd.com/maths/indices-intro.php
    Thanks guys, I get it now.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 23, 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.