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Factorisation

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Cosmas
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Factorisation [#permalink] New post   07 Jun 2012, 01:29
Can someone please help factorize x^3 + 2x^2 = 3x.

Is it not (x+3)(x+1)(x-1)

I don't seem to get why its x(x + 3)(x – 1) :lol:



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Re: Factorisation [#permalink] New post   07 Jun 2012, 01:35
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x^3 + 2x^2 = 3x

x^3 + 2x^2 - 3x = 0

x ( x^2 + 2x -3 ) = 0

x ( x^2 + 3x - x - 3 ) = 0

x [ x(x+3) - 1(x+3) ] = 0

x(x+3)(x-1) = 0
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Re: Factorisation [#permalink] New post   07 Jun 2012, 21:49
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Cosmas wrote:
Can someone please help factorize x^3 + 2x^2 = 3x.

Is it not (x+3)(x+1)(x-1)

I don't seem to get why its x(x + 3)(x – 1) :lol:



Do it step by step

x^3 + 2x^2 = 3x

transfer 3x to the other side we have

x^3 + 2x^2 - 3x = 0

we have a common factor of x among the three, as such we have

x (x^2 + 2x - 3) = 0

Now we can still factor x + 2x - 3 into

(x + 3) (x - 1)

if you are having a hard time to believe me, let's use FOIL:

x*x + 3x - 3 - 1*x = x^2 + 2x - 3

Got it?

That's why we have:

x (x + 3) (x - 1)
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Re: Factorisation [#permalink] New post   07 Jun 2012, 23:13
Clearly answered already, but I'll give it a go:

x^3 + 2x^2 = 3x
x^3 + 2x^2 -3x = 0
x * (x^2 + 2x - 3) = 0
x * (x+3) * (x-1) = 0

Voila. I've always struggled with factorization as well. Usually once I get to the quadratic stage, I just do trial and error (i.e., from x^2 + 2x - 3 to (x+3)(x-1)). Is there a quicker method?
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Re: Factorisation [#permalink] New post   07 Jun 2012, 23:28
I get it now. Thanks buddies! I figured that i have to factorise (x^2 + 2x - 3) as well.

gmatsaga wrote:
Cosmas wrote:
Can someone please help factorize x^3 + 2x^2 = 3x.

Is it not (x+3)(x+1)(x-1)

I don't seem to get why its x(x + 3)(x – 1) :lol:



Do it step by step

x^3 + 2x^2 = 3x

transfer 3x to the other side we have

x^3 + 2x^2 - 3x = 0

we have a common factor of x among the three, as such we have

x (x^2 + 2x - 3) = 0

Now we can still factor x + 2x - 3 into

(x + 3) (x - 1)

if you are having a hard time to believe me, let's use FOIL:

x*x + 3x - 3 - 1*x = x^2 + 2x - 3

Got it?

That's why we have:

x (x + 3) (x - 1)




Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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Re: Factorisation [#permalink]
07 Jun 2012, 23:28
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