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PostPosted: Thu Jun 07, 2012 11:11 am 
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Joined: Sun Oct 23, 2011 3:55 am
Posts: 33
Hello

Could somebody tell me how to work out the following please?

(2j - 7k) (3j + 4k)


Thanks


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PostPosted: Thu Jun 07, 2012 11:14 am 
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(2j - 7k) (3j + 4k) is not 11+ stuff

(2j - 7k) (3j + 4k) = 2j (3j + 4k) -7k (3j + 4k) etc

can't write it out properly as no superscripts


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PostPosted: Thu Jun 07, 2012 11:21 am 
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Thank you for your help with that, makes sense now! Been trying that for ages..... :roll:


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PostPosted: Mon Jun 11, 2012 11:51 am 
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Joined: Sun Mar 18, 2012 5:30 pm
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(a-b)(c-d)= ac-bc-ad+bd

Watch out for the change in signage though...2 minuses becoming a plus

This is Year 7 algebra, not 11+ entrance standard


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PostPosted: Mon Jun 11, 2012 4:56 pm 
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Paramjeet - it is not a good idea to say 'two minuses make a plus' because that gives problems when you calculate - 5 - 8 and children think the answer is + 13!


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PostPosted: Tue Jun 12, 2012 11:52 am 
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hi, yep your right as always.

I teach my child that when you have 2 minues, you add and put the sign of the minus. In the example quoted, it did not warrant it.


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