Simple Additional Maths AQA GCSE problem

Announcements Posted on
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hey there guys, need some help

    Work out the values of a and b so that ;

     4(x-5) + 4(7x+a) = b(8x-3)

    Thanks,
    PS I need an answer for A and B :cool:
    Offline

    0
    ReputationRep:
    (Original post by user)
    Hey there guys, need some help

    Work out the values of a and b so that ;

     4(x-5) + 4(7x+a) = b(8x-3)

    Thanks,
    PS I need an answer for A and B :cool:
    Just multiply out both sides:

     4(x-5) + 4(7x+a) = b(8x-3) 



4x - 20 + 28x + 4a = 8bx - 3b



32x + 4a - 20 = 8bx - 3b

    Now look at the x terms on both sides:

     32x = 8bx

    You can work out b from this; next look at the number terms:

     4a - 20 = -3b

    Substitute in your value for b, and you'll get what a is
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by cantstop-x)
    Just multiply out both sides:

     4(x-5) + 4(7x+a) = b(8x-3) 



4x - 20 + 28x + 4a = 8bx - 3b



32x + 4a - 20 = 8bx - 3b

    Now look at the x terms on both sides:

     32x = 8bx

    You can work out b from this; next look at the number terms:

     4a - 20 = -3b

    Substitute in your value for b, and you'll get what a is

    Thanks, but i dont understand how

     32x = 8bx

    surely 32x and 8bx are two different entititys due to there being different coefficients :/
    Offline

    0
    ReputationRep:
    (Original post by user)
    Thanks, but i dont understand how

     32x = 8bx

    surely 32x and 8bx are two different entititys due to there being different coefficients :/
    But the LHS expression is equal to the RHS expression. So the x terms must be equal. That's how I see it anyway.

    I'll see if anybody tells me if I'm doing it wrong though, it's always possible It just was the only way I could think of solving it!
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by cantstop-x)
    But the LHS expression is equal to the RHS expression. So the x terms must be equal. That's how I see it anyway.

    LHS AND RHS..
    Surely thats Congruency, thats got nothing to do with it :/

    And i think your workings are right the answer is
    a=2
    b-4
    So you are going about it the right way i think..
    The markschweme says 32=8b :/
    Offline

    0
    ReputationRep:
    (Original post by user)
    LHS AND RHS..
    Surely thats Congruency, thats got nothing to do with it :/

    And i think your workings are right the answer is
    a=2
    b-4
    So you are going about it the right way i think..
    The markschweme says 32=8b :/
    I would have thought it has everything to do with it. You're not solving the equation, you're making it valid with particular values for a and b, so the right thing to do would be to say the LHS should be equivalent to the RHS?

    And the markscheme would say that because it's comparing the coefficients of the x terms, you don't need to write in the xs
    • Thread Starter
    Offline

    0
    ReputationRep:
    BUMP!!

    Really confused, can someone please break down this problem in lehmans terms :/
    Offline

    3
    ReputationRep:
    Osma bin laden is aliveeee lets work out lhs and rhs of him.
    Offline

    0
    ReputationRep:
    You're not going to get an A* with distinction at this rate...
    Offline

    3
    ReputationRep:
    Im ****in gassed boy mans gonna get A* in additionalansj matrhs. and i rock beccuseje i go to skengeness *****es haaa dey got paper for me n i no questions !!!!
    Offline

    3
    ReputationRep:
    bob i h8 you Loooool
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by khalidpatel)
    bob i h8 you Loooool
    Gasman
 
 
 
Write a reply… Reply
Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: June 18, 2011
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Today on TSR
Poll
How are you feeling about doing A-levels?
Study resources

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

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