Today we looked at factorising by grouping. This involves grouping the terms of an expression into pairs and factorising each pair individually. For example:
2ax + 8ay + cx + 4cy
We can group the 2ax and the 8ay together, as well as the cx and the 4cy.
If we look at the first group (2ax and 8ay), we see a common factor of 2a. If we take this out to factorise we get: 2a(x + 4y)
If we look at the second group (cx and 4cy) there is a common factor of c. If we take this out to factorise we get: c(x + 4y)
Now that we have factorised each group, we can go and put them back into the expression in their factorised form. We then get:
2a(x + 4y) + c(x + 4y)
We can now see a common factor of (x + 4y) in this expression. If we take this out and factorise, we get:
(x + 4y)(2a + c) which is our fully factorised final answer.
If you are unsure as to how we factorise, see my previous post below.
If you want more information on this, have a look here: http://www.khanacademy.org/math/algebra/multiplying-factoring-expression/factoring-by-grouping/v/factoring-trinomials-by-grouping-1 -> really good video on this topic!
or here: http://www.compuhigh.com/demo/factoringinpairs.htm
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