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factorising help

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    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
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    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?
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    (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
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    (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.
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    (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.
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    (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)
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    (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.
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    (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
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    (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
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    (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"
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    (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
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    (Original post by zed963)
    I will ask
    Good

    You need someone to sit down with you on this
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    (Original post by zed963)
    I will ask
    Here is one way that might help. Let A = x + 3y
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    (Original post by steve2005)
    Here is one way that might help. Let A = x + 3y




    Uploaded with ImageShack.us
    Awesome you made me understand.
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    (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
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    So how would I do 50(2x+1)^2-18(1-x)^2
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    (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
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    (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
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    (Original post by zed963)
    ? I didn't understand what u meant
    That's why she suggested that YOU should expand the brackets first.
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    So would it be 200x+1 -18-18x^2
 
 
 
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