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factorising help

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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Reply 1
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?
Reply 2
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
Reply 3
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.
Reply 4
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.
Reply 5
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)
Reply 6
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.
(edited 11 years ago)
Reply 7
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/showthread.php?t=1969289
(edited 11 years ago)
Reply 8
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/showthread.php?t=1969289


I asked about the algebraic fraction one
Reply 9
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"
Reply 10
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
Original post by zed963
I will ask


Good :smile:

You need someone to sit down with you on this
Original post by zed963
I will ask
Here is one way that might help. Let A = x + 3y
(edited 11 years ago)
Reply 13
Original post by steve2005
Here is one way that might help. Let A = x + 3y




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Awesome you made me understand.
Reply 14
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
Reply 15
So how would I do 50(2x+1)^2-18(1-x)^2
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




It might be easier for you to expand and simplify
(edited 11 years ago)
Reply 17
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
Original post by zed963
? I didn't understand what u meant


That's why she suggested that YOU should expand the brackets first.
Reply 19
So would it be 200x+1 -18-18x^2

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