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Help with "expand and simplify expression" question please
Posted: Thu Jun 07, 2012 12:11 pm
by devonmum
Hello
Could somebody tell me how to work out the following please?
(2j - 7k) (3j + 4k)
Thanks
Re: Help with "expand and simplify expression" question plea
Posted: Thu Jun 07, 2012 12:14 pm
by Guest55
(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
Re: Help with "expand and simplify expression" question plea
Posted: Thu Jun 07, 2012 12:21 pm
by devonmum
Thank you for your help with that, makes sense now! Been trying that for ages.....
Re: Help with "expand and simplify expression" question plea
Posted: Mon Jun 11, 2012 12:51 pm
by Paramjeet
(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
Re: Help with "expand and simplify expression" question plea
Posted: Mon Jun 11, 2012 5:56 pm
by Guest55
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!
Re: Help with "expand and simplify expression" question plea
Posted: Tue Jun 12, 2012 12:52 pm
by Paramjeet
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.