Difference between revisions of "Common factorizations"

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These are a few special common factorizations, please add more:
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== Basic Factorizations ==
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These are basic factorizations that are used all the time.  These should be memorized, but you one should also know where they are derived from.
  
 
*<math>\displaystyle x^2-y^2=(x+y)(x-y)</math>
 
*<math>\displaystyle x^2-y^2=(x+y)(x-y)</math>
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*<math>\displaystyle x^3-y^3=(x-y)(x^2+xy+y^2)</math>
 
*<math>\displaystyle x^3-y^3=(x-y)(x^2+xy+y^2)</math>
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== Vieta's/Newton Factorizations ==
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These factorizations are useful for problem that could otherwise be solved by [[Newton sums]] or problems that give a polynomial, and ask a question about the roots.  Combined with [[Vieta's formulas]], these are excellent factorizations that show up everywhere.
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*<math>\displaystyle (a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ac)</math>
  
 
*<math>\displaystyle (a+b+c)^3=a^3+b^3+c^3+3(a+b)(b+c)(a+c)</math>
 
*<math>\displaystyle (a+b+c)^3=a^3+b^3+c^3+3(a+b)(b+c)(a+c)</math>
  
More common factorizations can be found [http://tutorial.math.lamar.edu/pdf/Algebra_Cheat_Sheet_Reduced.pdf here].
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== Other Resources ==
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* [http://tutorial.math.lamar.edu/pdf/Algebra_Cheat_Sheet_Reduced.pdf More Common Factorizations].

Revision as of 16:09, 20 June 2006

Basic Factorizations

These are basic factorizations that are used all the time. These should be memorized, but you one should also know where they are derived from.

  • $\displaystyle x^2-y^2=(x+y)(x-y)$
  • $\displaystyle x^3+y^3=(x+y)(x^2-xy+y^2)$
  • $\displaystyle x^3-y^3=(x-y)(x^2+xy+y^2)$


Vieta's/Newton Factorizations

These factorizations are useful for problem that could otherwise be solved by Newton sums or problems that give a polynomial, and ask a question about the roots. Combined with Vieta's formulas, these are excellent factorizations that show up everywhere.

  • $\displaystyle (a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ac)$
  • $\displaystyle (a+b+c)^3=a^3+b^3+c^3+3(a+b)(b+c)(a+c)$

Other Resources