Britney S.

asked • 03/02/16

could someone please help me?

Factor the following.

3r^2-12
 
i thought it was 3r(r-4) but i got it wrong :(

Kenneth S.

First rule of factoring: isolate GREATEST COMMON FACTOR (GCF).
 
Then look at polynomial:  Is it the Difference of Squares (applies to some binomials)
Is it the Difference of Cubes? Is it the Sum of Cubes? (can apply to some binomials)
Is it a trinomial that can be factored as the Product of two binomials? (this is a key skill that you'll be learning in Algebra, and its a very important one, which applies VERY FREQUENTLY IN ALL FUTURE MATHEMATICS.
 
Note: Factoring a trinomial (if possible) is the art of un-FOIL-ing.
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03/02/16

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Eric C. answered • 03/02/16

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Hi Britney.
 
You were close! But in order to factor out an "r" both terms need to have r in them. Unfortunately your 12 doesn't.
 
Just factor out a 3 for now:
 
3*(r^2 - 4)
 
Now you can recognize that (r^2 - 4) is a perfect square, so it can be factored even further:
 
3*(r+2)(r-2)
 
Hope this helps!
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