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# Factorisation... watch

1. Hi guys,

I need help to factorise this very easy expression:

x^2-4

Thanks
2. (Original post by Sophie Maywood)
Hi guys,

I need help to factorise this very easy expression:

x^2-4

Thanks
complete the square!

(x-2)(x+2)

edit: difference of two squares...my mistake.
3. x^2 is x squared.

4 is a square number.

The subtraction means "difference".

Put this together and what do you realise?
4. Ah, so it's a difference of 2 squares, which means the coefficient of x cancel each other out, yes?
5. (Original post by Sophie Maywood)
Ah, so it's a difference of 2 squares, which means the coefficient of x cancel each other out, yes?
That's right. Expanding out (x-2)(x+2) will give you a +2x term and a -2x term.
6. Ok thanks !

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Updated: November 15, 2008
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