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Prime factorization

  1. Oct 27, 2004 #1
    Is there a method one can use to obtain the prime factorization of a certain number?

    For example:
    Find the prime factorization of 49 + 39. [MathFest 2004]

    I realize that I can re-write the expression as 29.29+39, but that's about as far as I can go. :cry:
     
  2. jcsd
  3. Oct 27, 2004 #2

    shmoe

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    Homework Helper

    For this specific number, notice it's a sum of cubes, [tex]4^9+3^9=(4^3)^3+(3^3)^3[/tex] and use the general formula for the sum of cubes. This breaks it into 2 factors nicely, both are much easier to deal with then the orignial. Just use trial division on these 2 factors to furthur break them down.
     
  4. Oct 27, 2004 #3
    I did use the sum of two cubes formula. This is what I got:
    64³+27³=(91)(64²-64.27+27²)=(7)(13)(4096-1728+729)=7.13.19.163

    That's the correct answer, but I had to multiply the second bracket out to get it. I was just wondering if there was some other way I could use that wouldn't involve this level of multiplication.
     
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