Polynomial division with unknowns - Oxford Mathematics Admissions Test 2017

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  • Опубликовано: 3 ноя 2024

Комментарии • 6

  • @RajSandhu-gm8iz
    @RajSandhu-gm8iz 2 месяца назад +4

    It was much easier to use the first equation to give b= -a²-a, sub this into the other equation leads to 2a^4-a²-1=0. Which is a hidden quadratic that leads to a=1 or -1, which leads to b =0 or -2.

    • @devotion7890
      @devotion7890 2 месяца назад +1

      I did it exactly the same way

    • @slytherinbrian
      @slytherinbrian 2 месяца назад +1

      Same!

    • @mathoutloud
      @mathoutloud  Месяц назад +1

      Yeah I saw this solution after recording and was surprised I didn’t get it that way on the first go.

    • @devotion7890
      @devotion7890 Месяц назад +1

      @@mathoutloud Haha, I'm often surprised myself at how “complicated” I solve various math problems, even though it would be much easier ;)

  • @dan-florinchereches4892
    @dan-florinchereches4892 Месяц назад +1

    This looks like a pain to go trough normally. I think i got some ideas
    Since x^-ax+a^4 = q(x)(x+b)+1
    X^2-ax+a^4-1= q(x)(x+b) plug in x=-b
    b^2+ab+a^4-1=0
    The s cond statement makes 1/a root of the polynomial given so:
    b/a^2+1/a+1=0
    b+a+a^2=0 so b=-a-a^2
    Verifying in the first relation:
    A^4+2a^3+a^2-a^2-a^3+a^4-1=0
    2a^4+a^3-1=0
    a^4. a^3. a^2. a. a^0
    Coef. 2. 1. 0. 0. -1
    -1. 2(-1)+1.
    2 -1. 1. -1. 0
    P(a)=(a-1)(2a^3-a^2+a-1)
    R'(x)= 6a^2-2a+1 has no real roots
    So there are only 2 values for a. a=1 b=0
    2a^3-a^2+a-1=0
    2a(a^2+a-a)-a^2+a-1=0
    -2ab -3a^2-3a+3a+a-1=0
    -2ab+3b+4a-1=0
    B=(1-4a)/(3-2a) so there are total 2 values of b one of which is 0