I need to know how to factor this

**Alienis Back** · September 22nd 2008, 04:59 AM

I don't know how to factor these four terms. I know factoring is all about finding factors but I need help to find out where that 3+x comes from and how can I do it.

**mr fantastic** · September 22nd 2008, 05:01 AM

Originally Posted by Alienis Back

I don't know how to factor these four terms. I know factoring is all about finding factors but I need help to find out where that 3+x comes from and how can I do it.

$x^3 + 3x^2 - 4x - 12 = x^2 (x+3) - 4(x+3)$ .

And you know how to factorise by taking out a common factor ...?

**Alienis Back** · September 22nd 2008, 05:50 AM

Sure I know. I had tried factoring all terms by x+3 and resulted too complicated. Didn't know you could consider them sepatately. Thanks.

**Shyam** · September 22nd 2008, 06:14 AM

Originally Posted by Alienis Back

I don't know how to factor these four terms. I know factoring is all about finding factors but I need help to find out where that 3+x comes from and how can I do it.

$x^3 + 3x^2 - 4x - 12 = x^2 (x+3) - 4(x+3)$

take common (x + 3)

$=(x+3)(x^2-4)$

Now, can you proceed further???

**Alienis Back** · September 22nd 2008, 01:00 PM

Thanks guys. I did it!

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