When is p^2-p+1 a Cube? | Balkan MO 2005

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  • Опубліковано 25 сер 2022

КОМЕНТАРІ • 23

  • @cassidoodledookevorkian274
    @cassidoodledookevorkian274 Рік тому +6

    Always the best math vids on UA-cam 👍

  • @richardfredlund8846
    @richardfredlund8846 Рік тому +1

    Amazing .. I love the way the logic flows.

  • @mathcanbeeasy
    @mathcanbeeasy Рік тому +3

    This is art. 🥰

  • @victorchoripapa2232
    @victorchoripapa2232 Рік тому +2

    Wowow... Nice exercise

  • @cassidoodledookevorkian274
    @cassidoodledookevorkian274 Рік тому +1

    🔥🔥

  • @Manisphesto
    @Manisphesto Рік тому +5

    Why do questions like the shape cube instead of x³?

  • @lo-fi_community
    @lo-fi_community Рік тому +1

  • @drynshockgameplays
    @drynshockgameplays 29 днів тому

    How would you choose the squares if you got something like m^4 + 3m^3 + ... with the cubic term

  • @jpolowin0
    @jpolowin0 Рік тому +2

    I suppose that 1 isn't counted as a prime. :-)

    • @alessiodaniotti264
      @alessiodaniotti264 Рік тому +3

      the definition of prime is based on non trivial divisibility/factorization, so unitary elements are never primes.

  • @JohnWick-hj4ep
    @JohnWick-hj4ep Рік тому +3

    Amazing! However i have a question if anyone could answer. I was able to follow most of it, but didn't understand how he chose the 2 close perfect squares, around 4:50 - 6:27.
    P.s tips about how to improve would also help :D

    • @Leardakhan3
      @Leardakhan3 Рік тому +2

      I think the strategy is to look at the higher order terms, since there is a^4 - 6a^2, he looked for (a^2 - 3)^2, then you can look for which values of a the linear term and the constant are higher or lower than each other, that is my take at least.

    • @bait6652
      @bait6652 Рік тому

      Radic has to be a square dictated by the 2 Pn terms of highest power.
      Its a bounding trick he often uses when Pn w/o sq repr. has to be square. Bound it to 2-3 values or soln doesnt exist. Look for his n^4 problems ...theres like 3 of them

    • @bosorot
      @bosorot Рік тому +1

      To make you feel better this is standard olympic math technique. No normal kids can think how to do this on the spot for the first time. They learnt and practice and practice ... . If you can do this technique invented on your own , then you are a genius .

  • @johns.8246
    @johns.8246 Рік тому +1

    So how about when is p^2-p-1 a cube? There's at least one obvious solution.

  • @piman9280
    @piman9280 Рік тому +1

    It's a short exercise to see that p = 19 produces 343, which is 7^3. Once again we have a problem whose only solution can be found by very simple mathematics. I still enjoyed the robust solution.

  • @bowlteajuicesandlemon
    @bowlteajuicesandlemon 7 місяців тому

    How do we know that if p divides (x²+x+1), then a factor of p-1 doesn't also divide (x²+x+1) which would mean (x-1) doesn't have to be divisible by p-1?

    • @saadhaider9576
      @saadhaider9576 5 місяців тому

      Because p-1 = (x^2+x+1) * ((x-1)/p)
      Since (x-1)/p is an integer, x^2+x+1 divides p-1

  • @harris5140
    @harris5140 Рік тому +1

    p=1 doesn't work? why?

    • @quanquin3822
      @quanquin3822 Рік тому +1

      1 is not prime.

    • @10names55
      @10names55 Рік тому

      You ment why not x=1
      Well p^2-p is always >0

  • @DontStudy
    @DontStudy Рік тому

    N9

  • @user-hq7hi2sl2o
    @user-hq7hi2sl2o Рік тому +1

    asnwer=1 os isit 🤣🤣🤣🤣