Factoring a Quadratic Expression: -6x^2 - 12x + 48

Quadratic equations and inequalities, variation equations, function notation, systems of equations, etc.
Aqua Dragon
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Factoring a Quadratic Expression: -6x^2 - 12x + 48

Postby Aqua Dragon » Sat Apr 11, 2009 3:50 pm

The problem I'm having is probably simple, but I can't figure out what I'm doing wrong.

I'm attempting to factor the equation -6x^2-12x+48 into the (x-a)(x-b) format. I managed to find that the two factors that would work would be -24 and 12, as multipled together they equal the product of -6 and 48 while when added together equal -12.

So I tried the box method to attempt to figure out the rest of the values

Code: Select all

      -6x        -24
-6x (-6x^2)     (-24x)
12   (12x)       (48)


By that, the solution should be (-6x-24)(-6x+12), but this is obviously not the case. -6x multiplied by -6x equals 36x^2, not -6x^2. Could someone tell me where I'm messing this up?

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Martingale
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Re: Factoring a Quadratic Equation

Postby Martingale » Sat Apr 11, 2009 4:10 pm

Aqua Dragon wrote:...
By that, the solution should be (-6x-24)(-6x+12), but this is obviously not the case. -6x multiplied by -6x equals 36x^2, not -6x^2. Could someone tell me where I'm messing this up?

you have an extra factor of -6 in your answer...you should have



or


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stapel_eliz
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Postby stapel_eliz » Sat Apr 11, 2009 5:49 pm

Aqua Dragon wrote:I tried the box method to attempt to figure out the rest of the values...

The "box" method works only after you've taken any common factors out front.

So your first step must be what was explained in the previous reply: take the -6 out front. Only then can you apply "box". :wink:

Aqua Dragon
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Re: Factoring a Quadratic Expression: -6x^2 - 12x + 48

Postby Aqua Dragon » Sun Apr 12, 2009 5:15 am

Ah, thank you atapel. Once I got that factor out of the way, I found the answer I wanted. Thanks. :thumb:


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