Tuesday, February 10, 2009

Reply to Franky

Hi Franky,

welcome to the blog! Regarding the question you mentioned in the earlier post:

....the factorisation thing like (3m-4n)(x+y) -(2m-3n)(x+y) so, the x+y is merged and become 1 x+y right.

You are moving ahead of lesson! Good!

Well, in factorisation, our objective is to identify common factors and take them out. In your example the expression (x + y) is common and we will take out this factor out. Then, we will group the rest of the terms together.

(3m-4n) (x+y) -(2m-3n) (x+y)
= ( x+ y ) [ (3m-4n) - (2m-3n) ]
= ( x + y ) ( 3m - 4n - 2m + 3n )
= (x + y) ( m - n )

In case you are wondering why -( 2m - 3n) becomes -2m + 3n, refer to the explanation below.

- ( 2m - 3n )

= (-1) (2m - 3n)
= (-1)(2m) - (-1)(3n) by distributive property
= - 2m + 3n

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