Can We Solve A Nonstandard Equation? 😮

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  • เผยแพร่เมื่อ 3 ต.ค. 2024
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ความคิดเห็น • 47

  • @josepherhardt164
    @josepherhardt164 3 หลายเดือนก่อน +44

    Before even viewing, I smell the obnoxious odor of Lambert's W function.

  • @neilmccafferty5886
    @neilmccafferty5886 3 หลายเดือนก่อน +9

    Two is clearly one solution. About two seconds to notice that.

  • @NirDagan
    @NirDagan 3 หลายเดือนก่อน +7

    After we guess x=2, we have to show that this solution is unique. Consider the function f(x)=x5^x. Note that for non positive x, f(x) is also non positive. and for positive x, f(x) is strictly increasing (no need to differentiate to see that). so there is a unique solution to our equation.

    • @schrysafis
      @schrysafis 3 หลายเดือนก่อน +1

      That's what I thought of instantly.

  • @scottleung9587
    @scottleung9587 3 หลายเดือนก่อน +1

    I got x=2 right away, but I could sense Lambert's W function being used just by looking at the original equation.

  • @dwm1943
    @dwm1943 3 หลายเดือนก่อน +2

    First impression: x = 2 is an obvious solution.
    If we sketch the graphs y = 5^x and y = 50/x it would seem there can only be the one intersection, therefore x = 2 is the only solution. Now I'll watch the video. I am sure there will be some subtlety that has escaped me. This is a wonderful channel.

    • @txikitofandango
      @txikitofandango 3 หลายเดือนก่อน

      It's clever to set y = 5^x, so y=50/x. The exponential function is increasing everywhere, and the rational function is decreasing everywhere, and both functions are continuous for x>0, so they have at most one point of intersection

    • @SyberMath
      @SyberMath  3 หลายเดือนก่อน

      good point!

    • @dwm1943
      @dwm1943 3 หลายเดือนก่อน

      @@SyberMath Lambert is ruining my life

  • @joyneelrocks
    @joyneelrocks 3 หลายเดือนก่อน +3

    Why use Lambert’s W Function when you can easily express that 50 = 2 * 25 = 2 * 5^2, meaning x = 2. It’s a similar process relative to using the W(), but much faster 😑

    • @maxgoldman8903
      @maxgoldman8903 3 หลายเดือนก่อน +2

      Because we’ve to confirm that 2 is the only solution. Sometimes we may get a complex solution via Lambert’s function. Taking derivative of x•5^x is to confirm 2 is the only real solution. This step is redundant if we’ve used Lambert’s function.

  • @wtspman
    @wtspman 3 หลายเดือนก่อน +2

    The prime factorization of 50 is 2*5^2. By 1:1 correspondence x = 2. It’s not “guess and check”.

    • @fahrenheit2101
      @fahrenheit2101 3 หลายเดือนก่อน

      Yes it is. Your logic is only valid if we were looking for integers x.

    • @FisicTrapella
      @FisicTrapella 3 หลายเดือนก่อน +1

      I did this. The following step is to know if there are more solutions; which is what Syber do at the end of the video. 👌

  • @SidneiMV
    @SidneiMV 3 หลายเดือนก่อน +3

    x5^x = (2)5²
    xe^(xln5) = (2)5²
    (xln5)e^(xln5) = (2ln5)5²
    (xln5)e^(xln5) = (ln5²)5²
    (xln5)e^(xln5) = (ln5²)(e^ln5²)
    xln5 = ln5² = 2ln5
    *x = 2*

    • @josepherhardt164
      @josepherhardt164 3 หลายเดือนก่อน +1

      Wonderful! And nary a W in sight! Good for you!

    • @SidneiMV
      @SidneiMV 3 หลายเดือนก่อน

      @@josepherhardt164 exactly. also Lambert W function would be useful

  • @Jonasz314
    @Jonasz314 3 หลายเดือนก่อน +1

    I don't quite get why you try to do this dance inside the W function. You can start from the start by saying 50 = 2*25, and recognize that 25 = 5^2. So you rewrite the equation as x * 5^x = 2 * 5^2
    Since the function on the left side is trvially increasing, there's only a single solution for x > 0, you can immediately see that x = 2 is the solution.

  • @roberttelarket4934
    @roberttelarket4934 3 หลายเดือนก่อน +1

    "t"(tea) or coffee. Ha ha I love it! Better than to "b" or not to be!

    • @SyberMath
      @SyberMath  3 หลายเดือนก่อน +1

      🫖

  • @terryendicott2939
    @terryendicott2939 3 หลายเดือนก่อน

    Use Desmos and graph y= x*5^x - 50.

  • @lijiancz2066
    @lijiancz2066 3 หลายเดือนก่อน

    5^(x5^x)=(5^x)^(5^x)=5^50=25^25 therfore, 5^x=25 x=2

  • @joannasi8386
    @joannasi8386 3 หลายเดือนก่อน

    I think we can also find the solution factoring the right side od the equation and easily proove the funtion is monotonic finding its derivative as always positive, what causes only one possibile solution found by factoring😁

  • @fahrenheit2101
    @fahrenheit2101 3 หลายเดือนก่อน

    The function is strictly increasing and continuous, so it's invertible, so the obvious real solution is unique in the reals. But if you want complex solutions also, then lambert W is obviously the correct approach

  • @dawnwing8597
    @dawnwing8597 3 หลายเดือนก่อน

    x.5^x =50
    Let x=1, 1x5!=40
    Let x=2, 2x5^2 = 50
    Just a easy sum, nothing complicated
    Until more than 5 terms come

  • @tanbw922
    @tanbw922 3 หลายเดือนก่อน

    You can see it immediately that x=2.

  • @RealPersistences
    @RealPersistences 3 หลายเดือนก่อน +2

    Seems like this is overcomplicating it to me..

  • @giuseppemalaguti435
    @giuseppemalaguti435 3 หลายเดือนก่อน +1

    x=W(50ln5)/ln5

  • @nasrullahhusnan2289
    @nasrullahhusnan2289 3 หลายเดือนก่อน

    x×5^x=50 --> 5×5^x=2×5²
    Thus x=2

  • @roberttelarket4934
    @roberttelarket4934 3 หลายเดือนก่อน

    "t"(tea) or coffee. Ha ha I love it! Better than to "b" or not to be!

    • @SyberMath
      @SyberMath  3 หลายเดือนก่อน

      ☕️

  • @_Rainbooow
    @_Rainbooow 2 หลายเดือนก่อน

    so damn easy

  • @syed3344
    @syed3344 3 หลายเดือนก่อน

    x.5^x=2.25
    x.5^x=2.5²
    x=2

  • @louf7178
    @louf7178 3 หลายเดือนก่อน

    8:30 Go through all these * hoops * . Not "loopholes".

  • @Darisiabgal7573
    @Darisiabgal7573 3 หลายเดือนก่อน

    2 * 5^2 = 50 ho-hum

  • @chasmosaurus3
    @chasmosaurus3 3 หลายเดือนก่อน

    Since x=2, you are on the upper real branch of the Lambert function. There is only one solution and it is real.

  • @xd19592
    @xd19592 2 หลายเดือนก่อน

    Un un um!!

  • @rakenzarnsworld2
    @rakenzarnsworld2 3 หลายเดือนก่อน

    x = 2

  • @vladimirkaplun5774
    @vladimirkaplun5774 3 หลายเดือนก่อน

    🤑

    • @SyberMath
      @SyberMath  3 หลายเดือนก่อน

      😜

  • @peskarr
    @peskarr 3 หลายเดือนก่อน

    f=x*5^x is monotonically increasing, so here is only one solution, and it is x=2 obviously, why does video last 10 minutes?

    • @LucasLee-vq2lv
      @LucasLee-vq2lv 2 หลายเดือนก่อน +1

      if he replace the 5 with a 4, people should complain that it is not a whole number. The video is titled Can We Solve a Nonstandard Equation and he used a method that should work for any numbers. The video is not titled how to solve this specific equation; it is just how to solve this type of equation.