**Problem / Question**

**Solution**

**Commentary**

Here I illustrate the usefulness of
chunking to

(3

*factorise*(AmE:*factor*) an algebraic expression. Observe that 3*a*– 2*b*is a repeated part of the expression. I call it a “chunk”. To make it clear, I rewrite (3*a*– 2*b*)² as (3*a*– 2*b*)(3*a*– 2*b*) so that you can see it as two copies of the same chunk. I highlight in yellow one copy of (3*a*– 2*b*) from each of(3

*a*– 2*b*) (3*a*– 2*b*) and -3(3*a*– 2*b*). The remaining stuff are highlighted in blue and green. Take out the yellow chunk as common factor by writing it out on the left in the third line, shown in yellow. You can pull out the common factor by writing it out to the right if you want, but here I chose to put it on the left. The result would be equivalent anyway. Once you have written out the common factor, you write out the other stuff (shown highlighted in blue and green) into another other bracket.
Once you understand how it works, you can
actually do the second line mentally and write down the answer straightaway. Chunking is a very useful technique in
mathematics. Here are some more examples
of the technique of chunking: (1),
(2),
(3).

H04. Look for
pattern(s)

H10. Simplify
the problem

H11. Solve part
of the problem

**Suitable Levels**

*****Lower Secondary Mathematics (Sec 1 ~ grade 7)

*****GCE ‘O’ Level “Elementary” Mathematics

* other syllabuses that involve algebra and
factorisation (factoring)

* any learner who is interested
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