How to factor a 5-term polynomial (the double-cross method)

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  • Опубліковано 20 гру 2024

КОМЕНТАРІ • 29

  • @Iomhar
    @Iomhar 9 місяців тому +10

    6a+2b=-11
    Lef side is even, right side is odd!
    No integer solution!

  • @nevoitzhak2092
    @nevoitzhak2092 6 місяців тому +7

    The sum of the coefficients is 0 therefore 1 is a solution
    X⁴-4x³+2x²-11x+12=
    X⁴-x³-3x³+3x²-x²+x-12x+12=
    X³(x-1)-3x²(x-1)-x(x-1)-12(x-1)=
    (X-1)(x³-3x²-x-12)
    Then factoring a cubic is much easier

  • @a_man80
    @a_man80 3 місяці тому +2

    My solution: x^3*(x-4)+(2x-3)(x-4)=(x-4)(x^3+2x-3)=(x-4)(x-1)(x^2+x+3) first factor out x^3 from first two terms, then factorize remaining second degree polynomial, then factor out (x-4), i found the x-1 factor by trying in my head

  • @JoseAntonio-ng5yu
    @JoseAntonio-ng5yu 6 місяців тому

    If the independent term has too many factors, this can be quite hard, as you must check every combination of two factors 2 times each, as they can also have switched signs.
    The solution of the system of equations is a=(Ac-C)/(c-d) and b=(C-Ad)/(c-d). A and C are the coefficients of x^3 and x, and c and d are the top and bottom numbers at the right cross which are factors of the independent term. Substitute directly into a to eliminate more quickly those in which a is not a in integer. If a is an integer, obtain b and check the last condition

  • @giorgouis9642
    @giorgouis9642 6 місяців тому +1

    could you do the Δ(4th/D) problem from the Greek panhellenics 2024 if possible?

  • @lushleafy1174
    @lushleafy1174 9 місяців тому +6

    this is harder than the synthetic division method, i don't this i can use this method efficiently, i am too dumb

    • @apotatoman4862
      @apotatoman4862 9 місяців тому

      me too

    • @Orillians
      @Orillians 6 місяців тому

      Isnt synthetic division only for cubics?

    • @bruhbro9813
      @bruhbro9813 6 місяців тому +1

      ​@@Orillians It's actually for any polynomial

    • @Orillians
      @Orillians 6 місяців тому

      @@bruhbro9813 damn thank you!

    • @goliath6278
      @goliath6278 6 місяців тому +3

      Not all 4th degree polynomials can be factored with synthetic division. If all the roots are imaginary, then synthetic division can't help, and a method like this might be the only way.

  • @dutchie265
    @dutchie265 6 місяців тому

    2:30 why do a and b need to be whole numbers? Is there a rule for that?

    • @JoseAntonio-ng5yu
      @JoseAntonio-ng5yu 6 місяців тому +3

      Being a monic equation with integer coefficients, it can't have factors with fraccional coeficients

  • @major__kong
    @major__kong 6 місяців тому +1

    (x - r1)(x - r2)(x - r3)(x - r4) = ax^4 + bx^3 + cx^2 + dx + e
    Multiply out the left side, set the coefficients of like powers of x equal to each other, solve the system of equations for a, b, c, d, and e in terms of r1, r2, r3, and r4. Hint: a = 1. :-)

  • @Ben_Long
    @Ben_Long 6 місяців тому

    Do you have a video on lots of different ways to factor different polynomials?

    • @NadiehFan
      @NadiehFan 6 місяців тому

      ua-cam.com/video/yx2RetjV1Bo/v-deo.html
      ua-cam.com/video/55ufNfFofzY/v-deo.html
      ua-cam.com/video/B8dCd6PkHMY/v-deo.html

  • @wdobni
    @wdobni 6 місяців тому

    you should be able to calculate whether useful quantum computers will ever be developed....the limiting factor is noise and we know how much noise there is and how much each unit of noise reduces quantum integrity with respect to accuracy.....it should be a straightforward matter to compute whether noise will ever be sufficiently mastered to permit reliable useful quantum computing beyond the toy stage

  • @HoussamMoghrabi
    @HoussamMoghrabi 6 місяців тому

    (x−1)(x−3)(x2−2x+4) by long division

    • @z000ey
      @z000ey 6 місяців тому

      true, but to do long division don't you need to first guess either (x-1) or (x-3)?

    • @HoussamMoghrabi
      @HoussamMoghrabi 6 місяців тому

      @@z000ey this how I got (x-1) and (x-3) then I did long division and got my answer.

    • @JoseAntonio-ng5yu
      @JoseAntonio-ng5yu 6 місяців тому

      But you can't always do that

  • @aneeshbro
    @aneeshbro 6 місяців тому +1

    bro when are u gonna solve my problem? I need the answer, u explain everything in the best way possible.

  • @kadinatorgaming
    @kadinatorgaming 3 місяці тому

    Please help me factor 5x^4-7x^3+3x^2-x+1

  • @inyomansetiasa
    @inyomansetiasa 6 місяців тому

    Hello

  • @nuctang
    @nuctang 6 місяців тому

    X^6............. then (x^6........)(☠☠☠☠☠☠)