Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    if u have a modulus expression say

    l 3x+5 l = l 5x l

    do you have to square both sides to solve, or do you just treat the mod bit as brackets


    or wqhat if you have one\side with a modulus bit
    eg solve for x, in terms of a:
    3a = l x-(4x+a) l +a

    i get x= 2a(1-a)/(1-4a)

    could someone post some more examples with solutions of different types of mod equation questions
    Offline

    0
    ReputationRep:
    (Original post by hihihihi)
    if u have a modulus expression say

    l 3x+5 l = l 5x l

    do you have to square both sides to solve, or do you just treat the mod bit as brackets


    or wqhat if you have one\side with a modulus bit
    eg solve for x, in terms of a:
    3a = l x-(4x+a) l +a

    i get x= 2a(1-a)/(1-4a)

    could someone post some more examples with solutions of different types of mod equation questions
    you can square them or draw a graph,depends on how much algebra u want to do..............
    Offline

    1
    ReputationRep:
    (Original post by hihihihi)
    if u have a modulus expression say

    l 3x+5 l = l 5x l

    do you have to square both sides to solve, or do you just treat the mod bit as brackets


    or wqhat if you have one\side with a modulus bit
    eg solve for x, in terms of a:
    3a = l x-(4x+a) l +a

    i get x= 2a(1-a)/(1-4a)

    could someone post some more examples with solutions of different types of mod equation questions
    ² ³ ± ÷ ° √ ∂ ∞ ≈ ≠ ≡ ≥ ≤ ø Ø ½ ¼ « » µ π

    l 3x+5 l = l 5x l
    Square both sides:
    9x²+30x+25=25x²
    16x²-30x-25=0
    (8x+5)(2x-5)
    Therefore solutions are:
    x=-5/8 or x=5/2

    3a = l x-(4x+a) l +a
    2a = l x-(4x+a) l
    ±2a = x-(4x+a) therefore:

    3a+3x=0
    OR
    -a+3x=0
    Offline

    0
    ReputationRep:
    (Original post by Bhaal85)
    ² ³ ± ÷ ° √ ∂ ∞ ≈ ≠ ≡ ≥ ≤ ø Ø ½ ¼ « » µ π


    3a = l x-(4x+a) l +a
    2a = l x-(4x+a) l
    ±2a = x-(4x+a) therefore:

    3a+3x=0
    OR
    -a+3x=0
    I don't understand the ±2 in the bold bit??? Where did that come from
    Offline

    1
    ReputationRep:
    (Original post by Silly Sally)
    I don't understand the ±2 in the bold bit??? Where did that come from
    The modulus can be switched, e.g.

    a = l x l is the same as saying:
    ±a = x
    Offline

    0
    ReputationRep:
    (Original post by Bhaal85)
    The modulus can be switched, e.g.

    a = l x l is the same as saying:
    ±a = x
    ahh - i see! thanks!!!
    Offline

    1
    ReputationRep:
    (Original post by Silly Sally)
    ahh - i see! thanks!!!
    Though in the case of:

    l a l = l x l you can't do it.
    Offline

    13
    ReputationRep:
    (Original post by Bhaal85)
    Though in the case of:

    l a l = l x l you can't do it.

    WHY NOT?
    Offline

    1
    ReputationRep:
    l 3x+5 l = l 5x l
    Squaring both sides gives...

    9x^2 + 30x +25 = 25x^2
    Collecting like terms...

    16x^2 - 30x -25.

    Factorising...
    (8x + 5) (2x - 5)

    x = -5/8 or 5/2...

    So why was everyone jabbering about an a??? That's the method I would use...Drawing graphs is too time consuming and often far less accurate...
 
 
 
Turn on thread page Beta
Updated: June 19, 2004
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
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.