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# Factorisation - Method of Common Factors

#### notes

We begin with a simple example: Factorise 2x + 4.
We shall write each term as a product of irreducible factors;
2x = 2 × x
4 = 2 × 2
Hence 2x + 4 = (2 × x) + (2 × 2)
The factor 2 is common to both the terms.
Observe, by distributive law
2 × (x + 2) = (2 × x) + (2 × 2)
Therefore, we can write
2x + 4 = 2 × (x + 2) = 2 (x + 2)
Thus, the expression 2x + 4 is the same as 2 (x + 2).  Now we can read off its factors: they are 2 and (x + 2). These factors are irreducible.

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Method of common factors [00:05:43]
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