If you are factorising a number then you are looking for the factors, where factors are the numbers which when multiplied together give you the number you started with. Think of a number, any number. OK I have thought of one. It is 27. There are always four factors to any number 1 and that number, so for 27, 1 and 27 are factors. The other two factors are the equivalent numbers but this time with a negative sign, because a negative times a negative is a positive. So the two other factors of 27 are -1 and -27.

If I had chosen an even number there would have been other factors because 2 would have been there along with half the original number (and then you would have the same numbers but with negative signs). In the case of 27 there are also the factors 3 and 9. You can find this by trial and error. Obviously miss out all the even numbers. 5, 7, 11, 13 are not factors. It didn't take long to work that out so I now know that the only factors of 27 are 1,3, 9 and 27.

That sums it up

## Monday, 4 May 2009

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