A very nice olympiad maths question | Solve (x-3)^4=16 | You need to see this trick | Algebra

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  • Опубліковано 24 лис 2024

КОМЕНТАРІ • 48

  • @shannonmcdonald7584
    @shannonmcdonald7584 6 місяців тому +7

    Very nice. Sometimes, I have trouble getting started, and you always help me with that. From there, Ican solve.

    • @SpencersAcademy
      @SpencersAcademy  6 місяців тому +1

      Awesome! I am really happy to hear that.

  • @culater
    @culater 5 місяців тому +1

    Sweet 👍

  • @nerd5865
    @nerd5865 6 місяців тому +2

    or just u=x-3
    u^4=16
    recall if x^n=m, then x=nthroot(m) e^{2ikpi/m} where k is an integer
    u=2e^{ikpi/2}
    x-3=+-2, +-2i
    x=3+-2, 3+-2i

  • @rajasengannann63
    @rajasengannann63 6 місяців тому +3

    (x-3)^4=16
    Taking square root on both sides,
    (x-3)^2=+4 or (x--3)^2=-4
    If (x-3)^2=4 taking square root again, x-3=+2 or x-3= -2
    x=3+2=5 or x=3-2=1
    If (x-3)^2=-4 taking square root
    x-3=+ or - 2i
    If x-3= 2i then.x=3+2i
    If x-3 = -2i then x=3-2i
    So the solutions are
    5,3,3+2i and 3-2i

  • @caleboji4857
    @caleboji4857 6 місяців тому +2

    5 and 1 is the he answer. Actually got it in seconds
    16 is 4^2 which is the same as 2^4 or (-2)^4 then cancelling out 4 at the exponent at both sides x-3=2 or x-3=-2 and finally x=5 and 1

    • @CyberFlare-fn9kn
      @CyberFlare-fn9kn 6 місяців тому

      You miss out in imaginary solutions with such a method

    • @lechaiku
      @lechaiku 6 місяців тому

      @caleboji4857
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @marie-michelevallee8005
    @marie-michelevallee8005 5 днів тому

    (x-3)^4=16
    x=5
    5 - 3 = 2
    2^4 =16

  • @АндрейЛюбавин-э4щ
    @АндрейЛюбавин-э4щ 6 місяців тому +2

    1;5;3-2i;3+2i

  • @АлексейСаныч-ц2л
    @АлексейСаныч-ц2л 6 місяців тому +1

    [(x-3)²=y]
    y² = 16
    |y| = 4 -> y=4 or y=-4
    (x-3)² = 4; (x-3)² = -4
    [x-3=z]
    z²=4; z²=-4
    z=2; z=-2; z=2i; z=-2i
    x=2+3; x=-2+3; x=2i + 3; x= -2i + 3
    x=5; 1; 3+2i; 3-2i

  • @davidbrown8763
    @davidbrown8763 6 місяців тому

    Observing that the 4th root of 16 is +/-2, I found the real roots, 1 and 5, by inspection.
    Finding the remaining 3 roots requires a considerable amount of extra work, which the video demonstrated.

    • @SpencersAcademy
      @SpencersAcademy  6 місяців тому +1

      That's a nice observation. I must commend you for that.

    • @davidbrown8763
      @davidbrown8763 6 місяців тому

      Many thanks. Have a nice day.
      NB. I neglected to state that the 4th root of 16 is +/- 2, not just 2, which I have now corrected. Hence x - 3 = 2, giving x = 5 and x - 3 = - 2, giving x= 1. That is how I was able to obtain the real roots by inspection.

  • @prasadrasikawidanagamachch3932
    @prasadrasikawidanagamachch3932 13 днів тому

    X=5 or 1 or (+/-) 2i+3

  • @Jacobsdonkiesjot1963
    @Jacobsdonkiesjot1963 6 місяців тому +1

    (X-3)4=2to 4
    X-3=2. X=5

    • @lechaiku
      @lechaiku 6 місяців тому

      @psycholoogdrs.hansjacobs9816
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @nikhileshkumaryadav6010
    @nikhileshkumaryadav6010 6 місяців тому

    (X-3)^4= 2^4
    X-3 = +-2
    X=3+2
    Or X=3-2

  • @hlicj
    @hlicj 5 місяців тому

    two solutions are obvious: x=5 and x=1

  • @harrymatabal8448
    @harrymatabal8448 6 місяців тому +1

    5 and 1

    • @SpencersAcademy
      @SpencersAcademy  6 місяців тому +1

      You are right, man. But this is a fourth-degree equation. So, it was supposed to have four roots (values of x).

    • @lechaiku
      @lechaiku 6 місяців тому

      @harrymatabal8448
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @lourdesgracia6767
    @lourdesgracia6767 6 місяців тому

    (5-3)^4 = 16

  • @andryvokubadra2644
    @andryvokubadra2644 3 місяці тому

    (x-3)⁴ = 16
    x ?
    =========
    For real solution
    (x-3)⁴ = 16
    (x-3)⁴ = (±2)⁴
    x-3 = ±2
    x - 3 = 2 --> x = 5
    x - 3 = -2 --> x = 1
    x = 1 & 5 7:13

  • @ShimelesTeacher
    @ShimelesTeacher 6 місяців тому

    Look at this shorter method.
    (x-3)^4 = 2^4
    => x-3 = 2
    x = 2+3 = 5

    • @nerd5865
      @nerd5865 6 місяців тому

      1, 3+2i, 3-2i

    • @lechaiku
      @lechaiku 6 місяців тому

      @ShimelesTeacher
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @n.662
    @n.662 6 місяців тому +2

    X-3=+/-2

    • @lechaiku
      @lechaiku 6 місяців тому

      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @mohinkhan2503
    @mohinkhan2503 6 місяців тому

    6

  • @Nobody-kx4cs
    @Nobody-kx4cs 6 місяців тому

    Bro it could be done in seconds

  • @gregc.mariano9226
    @gregc.mariano9226 6 місяців тому

    The solution is too long.
    The shortest solution is to take the 4th root of both sides.
    Hence, X-3=2. X= 2+3=5; X=5.
    To check whether 5 is the correct value of X, substitute the X value to the original equation, (5-3)^4= 16, 2^4=16, 16=16.
    Therefore, 5 is the only value of X.

    • @lechaiku
      @lechaiku 6 місяців тому

      @gregc.mariano9226
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @doowadiwadi
    @doowadiwadi 6 місяців тому +1

    Way too over-complicated approach. And definitely not an Maths Olympiad question.

    • @SpencersAcademy
      @SpencersAcademy  6 місяців тому

      I would appreciate it if you would show me your approach.

    • @DrAbdulRehman1989
      @DrAbdulRehman1989 5 місяців тому

      Rewrite 16 as 2^4 and raise both sides to power 1/4; you will get: x-3 = 2

  • @Onoelo23gf
    @Onoelo23gf 6 місяців тому +1

    Too long. 4th root of LHS=±2; Hence x=1 or 5. i is not relevant here.

    • @SpencersAcademy
      @SpencersAcademy  6 місяців тому +2

      Remember, this is a fourth-degree equation.
      You don't just take the fourth root of both sides. If you do that, you're just gonna have just two values of x, instead of four.

    • @lechaiku
      @lechaiku 6 місяців тому

      @Onoelo23gf
      You always should remember that any power of x tells you how many solutions should be. In this particular case (x^4) there are 4 roots of a given equation.
      So we have 2 real solutions and 2 complex solutions. If you have the math problem where the domain of x is not specified, you must show all solutions. If the domain is x = R you can avoid the complex solutions.

  • @Vintheflipper14
    @Vintheflipper14 6 місяців тому

    X=5