Hey there Sign in to join this conversationNew here? Join for free

factorising help

Announcements Posted on
Study Help needs new mods! 14-04-2014
Post on TSR and win a prize! Find out more... 10-04-2014
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    Hi,

    I am struggling to answer this question


    6y(x+3y)+9(x+3y)^2

    I don't know how to fully expand this and factorise.


    help
    • 10 followers
    Offline

    ReputationRep:
    You have two terms: 6y(x+3y) and 9(x+3y)^2. To factorise, you need to look for common factors in both terms. 3 and (x+3y) are common factors so you can take them outside the expression. So you'll have this:

    3(x+3y)( ...... )

    Can your work out what will go inside the brackets?
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    (Original post by notnek)
    You have two terms: 6y(x+3y) and 9(x+3y)^2. To factorise, you need to look for common factors in both terms. 3 and (x+3y) are common factors so you can take them outside the expression. So you'll have this:

    3(x+3y)( ...... )

    Can your work out what will go inside the brackets?
    No the way I have been taught is to expand the brackets and then do it
    • 2 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    No the way I have been taught is to expand the brackets and then do it
    Have fun wasting your time.
    • 10 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    No the way I have been taught is to expand the brackets and then do it
    Sometimes it is useful to expand and then factorise but not in this case. Expanding this expression will make it harder to factorise and that could be the reason why you're having trouble with the question.

    I'm pretty sure that your teacher would expect you to factorise using the method I showed in my last post.
    • 13 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    No the way I have been taught is to expand the brackets and then do it
    You appear to have been taught 'wrong'. ALWAYS try and factorise by using the highest common factor. In this case the obvious factors to 'go outside' are 3(x+3y)
    • 5 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    No the way I have been taught is to expand the brackets and then do it
    Wow you have a retarded teacher.

    Take a factor of (x+3y) from every term so you get (x+3y)(6y+9(x+3y))
    Expand within the second bracket and collect the terms. Another factor can be taken out and that is 3, from the second bracket only.
    • 39 followers
    Offline

    ReputationRep:
    (Original post by uttamo)
    Wow you have a retarded teacher.
    I would not be so quick to criticise the teacher in this case


    (Original post by zed963)
    I don't know how to fully expand this and factorise.
    help
    Have you spoken to your teacher since we tried to help you with these

    Do not suggest that you have not been shown how to factorise these as we spent A LOT of time on them with you last weekend

    When you still did not understand we said that you should seek personal help at school

    So I ask again ... HAVE YOU?



    Before people waste too much time

    http://www.thestudentroom.co.uk/show....php?t=1969289
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    I would not be so quick to criticise the teacher in this case




    Have you spoken to your teacher since we tried to help you with these

    Do not suggest that you have not been shown how to factorise these as we spent A LOT of time on them with you last weekend

    When you still did not understand we said that you should seek personal help at school

    So I ask again ... HAVE YOU?



    Before people waste too much time

    http://www.thestudentroom.co.uk/show....php?t=1969289
    I asked about the algebraic fraction one
    • 39 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    I asked about the algebraic fraction one
    But not about this? ... in spite of the fact that you asked and asked last week but clearly did not "get it"
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    But not about this? ... in spite of the fact that you asked and asked last week but clearly did not "get it"
    I will ask
    • 39 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    I will ask
    Good

    You need someone to sit down with you on this
    • 13 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    I will ask
    Here is one way that might help. Let A = x + 3y
    Attached Thumbnails
    Click image for larger version. 

Name:	Screen shot 2012-04-21 at 21.56.26.png 
Views:	29 
Size:	12.0 KB 
ID:	143345  
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    (Original post by steve2005)
    Here is one way that might help. Let A = x + 3y




    Uploaded with ImageShack.us
    Awesome you made me understand.
    • 5 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    I would not be so quick to criticise the teacher in this case
    Yeah you're right lol I take it back
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    So how would I do 50(2x+1)^2-18(1-x)^2
    • 39 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    So how would I do 50(2x+1)^2-18(1-x)^2
    I would use the difference of 2 squares

    Spoiler:
    Show


    50(2x+1)^2 - 18(x-1)^2 = 2[5(2x+1) + 3(x-1)][5(2x+1) - 3(x-1)]

    Spoiler:
    Show
    2(13x+2)(7x+8)





    It might be easier for you to expand and simplify
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    (Original post by TenOfThem)
    I would use the difference of 2 squares

    It might be easier for you to expand and simplify
    ? I didn't understand what u meant
    • 112 followers
    Offline

    ReputationRep:
    (Original post by zed963)
    ? I didn't understand what u meant
    That's why she suggested that YOU should expand the brackets first.
    • Thread Starter
    • 20 followers
    Offline

    ReputationRep:
    So would it be 200x+1 -18-18x^2

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?

    this is what you'll be called on TSR

  2. this can't be left blank
    this email is already registered. Forgotten your password?

    never shared and never spammed

  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. By completing the slider below you agree to The Student Room's terms & conditions and site rules

  2. Slide the button to the right to create your account

    Slide to join now Processing…

    You don't slide that way? No problem.

Updated: April 26, 2012
Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.