Double and Triple Integrals

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  • เผยแพร่เมื่อ 28 พ.ย. 2024

ความคิดเห็น • 414

  • @schifoso
    @schifoso 5 ปีที่แล้ว +636

    You are such a great teacher.
    And I like how you use "we" instead of "you". Makes the student feel like they are not alone.

    • @MegaYoungscientist
      @MegaYoungscientist 4 ปีที่แล้ว +27

      I think it's great because even the professors still are students at the end of the day, because everyone is still learning more about their subjects.

  • @akuo0708
    @akuo0708 7 หลายเดือนก่อน +19

    this is the clearest explaining math video i've ever watched

  • @GiangTranAI
    @GiangTranAI 5 ปีที่แล้ว +747

    Best teachers so far: 3blue1brown and Professor Dave.

    • @hzkzg1614
      @hzkzg1614 4 ปีที่แล้ว +55

      You seriously wouldnt count sal or Patrickjmt?

    • @adityarajsrivastava6580
      @adityarajsrivastava6580 4 ปีที่แล้ว +110

      Blackpenredpen

    • @garethpienaar3119
      @garethpienaar3119 4 ปีที่แล้ว +45

      Professor Leonard is the best for me, by far

    • @gouravgope1367
      @gouravgope1367 4 ปีที่แล้ว +15

      Zach star

    • @jorge_cazares
      @jorge_cazares 4 ปีที่แล้ว +8

      For me, the best teachers so far are: Professor Gross, from MIT OCW Calculus Revisited, 3blue1brown, and Professor Dave

  • @buttersquids
    @buttersquids ปีที่แล้ว +29

    I was struggling a lot on understanding double integrals on a homework assignment, but this helped massively. Thanks Dave!

  • @theresaread6174
    @theresaread6174 3 ปีที่แล้ว +54

    Blessings upon you, Dave. Two minutes in and you’ve already made this make more sense than my instructor.

  • @coop_the_troop
    @coop_the_troop 4 ปีที่แล้ว +9

    Man I’m trying to learn first calculus, I was recommended this from a friend in the math field to help, it seems a bit to daunting, I wish I was I just good at math and actually understood what he is talking about most of the time

    • @ProfessorDaveExplains
      @ProfessorDaveExplains  4 ปีที่แล้ว +17

      Start the calculus playlist from the very beginning and all will make sense!

  • @ActionJaxonH
    @ActionJaxonH 5 ปีที่แล้ว +35

    This video is amazing. I’m self taught, going through Professor Leonard’s Calc 3 YT series course, and double and triple integrals are coming up in the very near future so I wanted to get a head start. This is totally logical and it just makes sense

    • @extremeforlife8563
      @extremeforlife8563 2 ปีที่แล้ว +1

      Thanks, I checked out the series after seeing your comment. It is more suited to what I am looking for. Really appreciate it man.

  • @gabrielamorais7185
    @gabrielamorais7185 2 หลายเดือนก่อน +3

    This was simply amazing. I have never seen a TH-cam teacher be that clear and easy to understand. Thank you soooo much!!! :D

  • @shaiyongcheng9721
    @shaiyongcheng9721 4 ปีที่แล้ว +7

    This video is better than 1 hour of lecture. Tq very much

  • @FlyByPC
    @FlyByPC 5 ปีที่แล้ว +37

    Great explanation!
    Of course, my inclination is still to hit it with a FOR loop...

  • @mavlonkarlsefni
    @mavlonkarlsefni 7 หลายเดือนก่อน

    I have a test tomorrow, and your video really helped me to understand integration more deeply. Thanks from Russia!

  • @mastershooter64
    @mastershooter64 5 ปีที่แล้ว +142

    So you can actually find the volume inside a tesseract niceees

    • @kek3324
      @kek3324 5 ปีที่แล้ว +21

      its a hypervolume

    • @JorgetePanete
      @JorgetePanete 5 ปีที่แล้ว +19

      @@kek3324 It's*

    • @doxo9597
      @doxo9597 5 ปีที่แล้ว +39

      Jorge C. M. I can tell you have a lot of friends.

    • @OneDerscoreOneder
      @OneDerscoreOneder 5 ปีที่แล้ว +8

      It’s just all the side lengths multiplied

    • @dinamosflams
      @dinamosflams 5 ปีที่แล้ว +8

      You can find both, the volume and the hypervolume of a tesseract. Although I think it's more difficult to grasp the concept of the volume of a tesseract

  • @mikepablo
    @mikepablo 4 ปีที่แล้ว +11

    Brilliant , wish I had this when I did maths so much clearer and simple, during lock down going though my old notes 30 years ago inspired me to study more

  • @aloischipfurutse5079
    @aloischipfurutse5079 3 ปีที่แล้ว +10

    I still don't understand why someone can dislike a video like this :( You are incredible!

    • @dellpi3911
      @dellpi3911 3 ปีที่แล้ว

      th-cam.com/video/IangXACFW48/w-d-xo.html

  • @melontusk7358
    @melontusk7358 4 ปีที่แล้ว +2

    I've finally done it. Thanks for your help, my good sir. I'm a lot more confident now.

  • @harishkumar-rn2mw
    @harishkumar-rn2mw 4 ปีที่แล้ว +30

    Hi Dave, I got confused in the part choosing lower bound and upper bound between 2 cuves. Pls explain..

  • @werkatfischer3183
    @werkatfischer3183 3 ปีที่แล้ว

    This is probably the best that this video could possibly have been made.

  • @sine4859
    @sine4859 3 ปีที่แล้ว +2

    wow i didnt expect integrals to have this much depth to them... how can you not love math, omg
    great video btw :)

  • @acemaster1877
    @acemaster1877 3 วันที่ผ่านมา

    Triple integrals don't calculate 4D hyperspace. They are just a different way of calculating 3D space when the area of the inside isn't increasing or decreasing linearly. You'd need a Quadruple integral to calculate hyperspace.
    Look it up for clarification. His reasoning sounds correct, but I double-checked it with a few sources, and they state that triple integrals only calculate 3D space.

  • @derekconn9950
    @derekconn9950 3 วันที่ผ่านมา

    The only thing is the first graph isn’t really a cube. The base is a square that is 1 unit on the x and 2 units in y but the height of the “cube” is the function of x and y. The way to think about it is like this, the integral uses the volume of a cube equation because in Cartesian coordinates that’s what it is. So like a cubes formula for volume = length x width x height, but here the function you are integrating is the height and the dx and dy values are the length and width of the base of the structure, the integrals limits form the base. Since the integral values are all numbers it forms a square but the height is variable based on the function. If it was just a normal cube the function you’d be integrating would be a number. What the integral is actually doing is creating an infinite amount of cubes all with different heights but the same base area dx dy and summing them all over the course of the square area projected out. The best way to picture it is to graph the function and then draw the square on the xy plane but then picture the square projecting upwards until it hits that function that’s the power of the integrals it allows you to take the volume of not a cube using the formula for a cube by just making infinitesimal cubes and adding their volumes together. What the total volume that we are finding is actually a shape that has a square base and the height is like a parabolic shape. The best way to picture it is to graph the function in 3d and picture the shape of the bounds on xy plane which in this case it’s a square and picture it’s height as the image of that square going up until it hits that 3d graph.

  • @wompwomf
    @wompwomf 3 ปีที่แล้ว

    whenever my dad checks up on me if im doing work, i just pull up your videos and he doesnt question it! thank you :D

  • @leedsoldat4189
    @leedsoldat4189 7 หลายเดือนก่อน

    A learner from Tanzania,🤝you are a good teacher ❤

  • @jocelyneavila6870
    @jocelyneavila6870 4 ปีที่แล้ว +1

    Thank you for the subtitles in English! It makes it much easier to follow-up.

  • @georgefan2977
    @georgefan2977 5 ปีที่แล้ว +8

    Thank you, that was one of the most straightfoward explaination!

  • @adristimaulidafauzi4418
    @adristimaulidafauzi4418 3 ปีที่แล้ว +1

    Finally I understand the sense behind these

  • @amaizasafdar9401
    @amaizasafdar9401 3 ปีที่แล้ว

    no word to explain your efforts may God reward this

  • @lemonhscott7667
    @lemonhscott7667 10 หลายเดือนก่อน

    Professor Dave, thank you so much for these resources! They've been a huge help to me in ODELA and Vector Calc. I'd be lost without you!

  • @johnsnow3444
    @johnsnow3444 8 หลายเดือนก่อน

    Was so thrilled when i did the double integral the other way from y/2 to (y)^1/2 and got the same answer! strangely that way took up less paper. Thanks for the solid content!

  • @Kiky_MedPhysicist
    @Kiky_MedPhysicist 3 หลายเดือนก่อน +1

    Thank you sir for your dedication and for making this free! 🙏

  • @millieh3179
    @millieh3179 5 ปีที่แล้ว +101

    Can you do a video on Green's, Stokes' and Gauss' Theorems?

    • @Preparing_and_Testing
      @Preparing_and_Testing 5 ปีที่แล้ว +4

      Could you send me notes of divergence theorem ?

    • @ProfessorDaveExplains
      @ProfessorDaveExplains  5 ปีที่แล้ว +84

      Millie all three of those are filmed, animated, uploaded, and to be released very soon!

    • @GeoRaphaelMichael
      @GeoRaphaelMichael 4 ปีที่แล้ว +1

      @lulu , your wicked tactics to paint real Christians ain't gonna work, people like you are the reason muslims conflate legitimate love lead criticism from people like David Wood and Robert Spencer with hatred from people like you and richard spencer.

    • @awesomecodeyay8382
      @awesomecodeyay8382 3 ปีที่แล้ว +2

      20UPH512_Geo Raphael Michael
      What was lulu’s comment about?

    • @ivoryas1696
      @ivoryas1696 ปีที่แล้ว

      ​@@GeoRaphaelMichael
      *_Bruh, what_*

  • @arkadiuszkapuscinski6345
    @arkadiuszkapuscinski6345 5 ปีที่แล้ว +3

    Integrals are the most usefull part of math. Engineering is the example for that. Love them.

    • @marcioamaral7511
      @marcioamaral7511 5 ปีที่แล้ว +8

      Don't forget differential equations which model pretty much every dynamic phenomena

  • @bryanwharton6692
    @bryanwharton6692 5 ปีที่แล้ว +27

    “Performing multiple integrations is not all that daunting, on the SURFACE!!” Haha

  • @NoctuaStrigiformes
    @NoctuaStrigiformes 5 ปีที่แล้ว +2

    Integrals are tight. You made it look super easy, barely an inconvenience.

  • @JeanfrankSartori-c9p
    @JeanfrankSartori-c9p ปีที่แล้ว +1

    You're the E of the mc²! Great lecture. Congrats.

  • @chroma9848
    @chroma9848 5 ปีที่แล้ว +9

    You're an excellent teacher, you truly are. I survived 1st year of engineering with your help. It would be nice if you can make videos on differential equations 😅

  • @danielvolinski8319
    @danielvolinski8319 3 ปีที่แล้ว +2

    14:30 The first example on the Checking comprehension is wrong: the internal integral boundaries should be from x+1 to 2x

  • @TemplarX2001
    @TemplarX2001 4 ปีที่แล้ว +3

    annnnnnnnnnnnnnd you have a new sub/ bingewatcher

  • @cboaitey99
    @cboaitey99 5 ปีที่แล้ว +4

    Thanks so much! I never understood this in my Engineering lectures, now it makes sense.

    • @os9458
      @os9458 5 ปีที่แล้ว +1

      Hi Rosal.can I know is this thing involve I'm grade 12 or higher grade .Because I'm going to do engineering too. Currently grade 12

    • @cboaitey99
      @cboaitey99 5 ปีที่แล้ว +1

      OsJ I’m not sure, I studied this in university.

  • @cd8836
    @cd8836 ปีที่แล้ว +1

    Thank you for the videos. They help a lot! I’ve had a mental block about these topics for decades.

  • @thefatcat1997
    @thefatcat1997 5 ปีที่แล้ว +5

    I wish i had u as my teacher during my btech...

  • @lilpotato5870
    @lilpotato5870 หลายเดือนก่อน +1

    So clear and comprehensible. Thanks!

  • @christosgolsouzidis1286
    @christosgolsouzidis1286 5 ปีที่แล้ว +15

    I thought that double integrals give the area of the surface of a function and triple integrals the volume of a function respectively

    • @tzonic8655
      @tzonic8655 4 ปีที่แล้ว

      Και εγώ ρε φίλε,έτσι δεν λέει και ο γκαρουτσος? 😂

    • @cyrex-niaz7798
      @cyrex-niaz7798 2 หลายเดือนก่อน

      Don't they?​@@tzonic8655

  • @andreacondello
    @andreacondello 2 ปีที่แล้ว

    that is amazing how clear you was

  • @alexanderkaiser89
    @alexanderkaiser89 2 ปีที่แล้ว +6

    Hi Professor Dave.
    I have a request that you may find interesting or not, it’s a mathematical one. I have always found it hard to understand “Inter-universal Teichmüller theory”, “The Collatz Conjecture”, and “The Birch and Swinnerton-Dyer Conjecture”. If you would make a video on one of these topics that would really help 😊
    I’m studying a Master’s in mathematics in Denmark. I’m sorry for my English, I’m not mothertongue in English.
    Btw, I love your content.

  • @itsme.01
    @itsme.01 ปีที่แล้ว +1

    In the first comprehension, when we move from 2 to 3 in x,then y=x+1 is lower to 2x . Why we consider here limit in y from 2x to (x+1)?

  • @martind1692
    @martind1692 2 ปีที่แล้ว +1

    8:26; why is Y (upper bound) = x ^2.
    Why choose x^2 over 2x.
    ----------
    And X upper bound =2x.
    Why choose 2x over x^2?
    I appreciate the answer☀️

    • @moosclesapex4643
      @moosclesapex4643 2 ปีที่แล้ว

      because x^2 is of greater value, duh

  • @ejticomon2004
    @ejticomon2004 ปีที่แล้ว +5

    Why is the y integral from x^2 to 2x and not 2x to x^2?

    • @lolzdatguy4987
      @lolzdatguy4987 8 หลายเดือนก่อน +4

      Lower relative to y

  • @JorgetePanete
    @JorgetePanete 5 ปีที่แล้ว +3

    1:37 I think there are counterexamples to that statement, but it works in general.

  • @nosirrahonline
    @nosirrahonline 2 ปีที่แล้ว

    Oh my god, thank you so much for this video. The videos that I get for my class gave me an example where both y and x's bounds were 1 so I didn't understand how she was doing it.

  • @ahmedrazim7567
    @ahmedrazim7567 3 ปีที่แล้ว

    Actually at 8:34, we get x = ±√y, x = -√y being the other half of the parabola. So we write x = √y .

  • @SMNAviation
    @SMNAviation 3 ปีที่แล้ว +2

    I consider the view count on this an insult. And an even greater one, that 52 people dare dislike it. Dave, your videos are amazing.

  • @leowalentiny1638
    @leowalentiny1638 หลายเดือนก่อน +4

    How do you know it goes from y=x^2 to y=2x why is one the lower curve and the other the higher curve?

    • @m4rzb4rz-qq3yq
      @m4rzb4rz-qq3yq 8 วันที่ผ่านมา +1

      Hope it's not to late. Look at the x axis, the one closest to it is the lower one

    • @leowalentiny1638
      @leowalentiny1638 8 วันที่ผ่านมา

      @@m4rzb4rz-qq3yq no, not too late😅, thank you very much!

    • @m4rzb4rz-qq3yq
      @m4rzb4rz-qq3yq 8 วันที่ผ่านมา

      @leowalentiny1638 no problem :)

    • @sakhamurithanmai4442
      @sakhamurithanmai4442 6 วันที่ผ่านมา

      My doubt is the curve which has higher y value at particular x value should be considered higher curve. So it should lie close to y axis I think...​@@m4rzb4rz-qq3yq

  • @ejimadam
    @ejimadam 5 หลายเดือนก่อน +1

    I don't understand which would be the lower curve and which would be the higher curve?

  • @Aaron-q9p4h
    @Aaron-q9p4h 4 หลายเดือนก่อน +1

    Thank you, so much

  • @MikiSiguriči1389
    @MikiSiguriči1389 ปีที่แล้ว

    good job Dave, you have explained this to me in a most understandable way possible, with clear color indications, thank you sir.

  • @mujtabanazeer8837
    @mujtabanazeer8837 หลายเดือนก่อน +1

    Thank You very much.
    But, what do you mean by lower curve to higher curve while setting the bound?

  • @encinaallaineharleya.8586
    @encinaallaineharleya.8586 ปีที่แล้ว

    We have a calc quiz tomorrow and this video sure helps, Thanks!

  • @annea1537
    @annea1537 10 หลายเดือนก่อน

    Danke sehr!!!
    🎊 beste Erklärung! Mit Abbildungen, klar und deutlich.
    ❤❤❤❤❤

  • @ramuganesan
    @ramuganesan 2 ปีที่แล้ว +2

    at 07:12 , how do you say that y runs from the lower curve to upper curve? sir i cant understand that point

  • @mkpr757
    @mkpr757 3 ปีที่แล้ว

    A video masterpiece. Grateful for the illustrations, painted a clearer picture in my mind...

  • @eskayML
    @eskayML ปีที่แล้ว +1

    I have a question please
    For the upper and lower bounds isn't the x² greater than 2x and why didn't it get placed at the upper bound instead?.

  • @SaleBabft
    @SaleBabft 4 หลายเดือนก่อน

    7:39 a mistake in limits integration of 2x and x² ?
    If 2x on the top and x² under of 2x => if x:1. 2(1),(1)² and if x:2 2(2),(2)² and if x:3 its undefined[ 2(3),(3)³] => 6,9

  • @kaymoneyalottoww4828
    @kaymoneyalottoww4828 9 หลายเดือนก่อน

    cool teacher, straight to the point

  • @dzdzdzdzdzmr8696
    @dzdzdzdzdzmr8696 ปีที่แล้ว +1

    I dont understand what he meant by lower curve and higher curve when setting the bounds at 7:08

  • @Jack-lp4jd
    @Jack-lp4jd ปีที่แล้ว +2

    Best explanation around. Though im still struggling to understand how taking the integral of the x-y plane in two different ways gives volume. So the area under the curve given from the first integral just happens to also equal the volume?

  • @Natearl13
    @Natearl13 หลายเดือนก่อน +2

    But can Professor Dave explain why my prof throws trigonometric bounds on the triple integrals like wtf why do you hate me

  • @someone________2502
    @someone________2502 2 ปีที่แล้ว +1

    Great video. Even though I only did high school calculus I could still follow what he is saying.

  • @stonerambo3982
    @stonerambo3982 ปีที่แล้ว +4

    I was only confused in one step it got cleared only within first 2 minutes...

  • @kirancp4758
    @kirancp4758 2 ปีที่แล้ว

    There is an error at 10.55. In the equation , it should be 2xpower4 not"8xpower4. Therefore the volume is 24. It is not a negative value

    • @rashikasookun3907
      @rashikasookun3907 2 ปีที่แล้ว

      No it's good.

    • @kirancp4758
      @kirancp4758 2 ปีที่แล้ว +1

      @@rashikasookun3907 Ya. I just made a silly mistake.

  • @100iqgaming
    @100iqgaming 5 หลายเดือนก่อน

    idea, you could create a new notation where a single integral sign is arc length, double is area and triple is volume

  • @junebugcomputer
    @junebugcomputer 5 ปีที่แล้ว +3

    You getting people through college

  • @rva1945
    @rva1945 7 หลายเดือนก่อน

    Is there any video that shows how integrals are applied in engineering, for example, for building a bridge, a dam, a building, etc?

  • @monhbatonon6333
    @monhbatonon6333 3 ปีที่แล้ว

    now this is what math should be about. Solving something real

  • @CharlieParis-g8o
    @CharlieParis-g8o 4 วันที่ผ่านมา

    In the example starting at 2:21 does this not just find the area of the surface in the x-y plane that is under the cube? I thought you would also have to integrate dz from 0 - z in order to calculate the volume of the shape?

  • @zaidbinghazi
    @zaidbinghazi 26 วันที่ผ่านมา +1

    KING

  • @pawanmarahatta5749
    @pawanmarahatta5749 6 หลายเดือนก่อน

    blessings upon you, Dave.

  • @winner1338
    @winner1338 5 ปีที่แล้ว +1

    finding boundaries are the hardest part

  • @cameronspalding9792
    @cameronspalding9792 5 ปีที่แล้ว +1

    If the double integral of the absolute value of f is finite: the order doesn’t matter: the double integral of f is the same regardless of order

  • @paulgbago4586
    @paulgbago4586 4 ปีที่แล้ว +4

    hello can explain how you take x^2 as the lowest value for a integral and another integral.
    what makes them the upper value on y and lowest value on x ?can you make it more clear cause i tried to find why but still cant find out .
    At first i thought it was cause the 2x function was above the x^2 from 0 to 2.
    thanks you

    • @yuel.5013
      @yuel.5013 4 ปีที่แล้ว +1

      You're right, depends on the sign. Solve sqrt(y) >= y/2, it's true on [0; 4].

  • @wheatlysparble7900
    @wheatlysparble7900 ปีที่แล้ว

    I wish we had you as our professor

  • @salehsalum5308
    @salehsalum5308 ปีที่แล้ว +1

    I need more details in triple integrals, it is hard to imagine in 4D

    • @mackb996yt3
      @mackb996yt3 ปีที่แล้ว +1

      It is impossible to imagine a 4d space literally

  • @Silwanos
    @Silwanos 2 ปีที่แล้ว

    oh men i wish i knew you back when i was taking Applied maths 2 in college

  • @sauravkr.mahato
    @sauravkr.mahato 2 ปีที่แล้ว

    Great Visualization of the figure formed by double integration
    Loved it !!

  • @darkwing2924
    @darkwing2924 2 ปีที่แล้ว

    Thanks for making calculus fun and interesting

  • @aceflamez00
    @aceflamez00 5 ปีที่แล้ว +6

    Wow that was easier then expected. Thank you for explaining it well.

  • @azadprasad856
    @azadprasad856 3 ปีที่แล้ว

    He does know all about science stuff......... professor Dave Explains ❤️❤️❤️🔥🔥🔥. I Love this😎

  • @davidschmidt5893
    @davidschmidt5893 4 ปีที่แล้ว +5

    Would love to see some diff eq stuff. You’re so easy to learn from

  • @prateek3828
    @prateek3828 ปีที่แล้ว

    I thank you dear sir for mentoring me . 🙏

  • @lordyabo9910
    @lordyabo9910 ปีที่แล้ว +1

    Can someone please explain why the curve y=2x is greater than the curve y=x^2? Thanks in advance!

  • @UntitledPanda
    @UntitledPanda 3 ปีที่แล้ว +2

    Is there a way to generate the f(x,y) equation knowing only the two equations y=x^2 and y=2x? I don't see the connection between these.

    • @carultch
      @carultch 2 ปีที่แล้ว

      Both of those examples are only 2-dimensional equations. You would need a 3-dimensional equation to determine f(x,y).

  • @the_kid777
    @the_kid777 ปีที่แล้ว

    Wanted the computation process for the two problems.

  • @thabolikotsi5765
    @thabolikotsi5765 5 ปีที่แล้ว +1

    awesome vid thanks im a fresher ive jusst started self learning ths topic ths will help wth understanding

  • @didyk3574
    @didyk3574 4 ปีที่แล้ว +2

    Hey dave can you graph this function in 3D f(x,y)=xy/(x^2-y^2) around the point(0,0)

  • @kamalnath4606
    @kamalnath4606 11 หลายเดือนก่อน +1

    love you professor dave

  • @clarkpeng1008
    @clarkpeng1008 5 ปีที่แล้ว +3

    what if the functions defining the bounds overlaps more then once? Like sin(x) and x/2 then how do you determine the lower and upper bound?

    • @ProfessorDaveExplains
      @ProfessorDaveExplains  5 ปีที่แล้ว +4

      Ooh that's a good question. I suppose in such a case you would split it up into multiple integrals.

  • @sukasuka402
    @sukasuka402 2 ปีที่แล้ว

    excuse me prof, why my answer evaluate 1 is -3/2, where i'm wrong?

  • @TTeach22
    @TTeach22 ปีที่แล้ว

    Great thought and too clear fellow style, I apricate your way of explains

  • @jackrubin6303
    @jackrubin6303 4 ปีที่แล้ว

    If you look at f(x,y) = 1+ 4xy example, if you just look at solid by itself and compute volume without using complex integration, for x = 1 (1-0), y = 2, (3-1), and z = 1 + (4*1*2) = 9, I get a volume of 1*2*9=18. Where did I got wrong?

  • @krishlapatra424
    @krishlapatra424 5 ปีที่แล้ว +1

    Really nice ... So clear concept.... Thank you professor Dave

  • @jaccckky8978
    @jaccckky8978 5 ปีที่แล้ว +6

    I don't know why I need to pay to go in the Uni after this video

    • @neuacc7462
      @neuacc7462 5 ปีที่แล้ว +8

      So they give you a paper stating your watched some yt videos