Induction Inequality Proof Example 1: Σ(k = 1 to n) 1/k² ≤ 2 - 1/n

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  • เผยแพร่เมื่อ 30 ก.ย. 2024
  • Induction proofs involving sigma notation look intimidating, but they are no more difficult than any of the other proofs that we've encountered!

ความคิดเห็น • 66

  • @blazept567
    @blazept567 10 ปีที่แล้ว +55

    lol i can truly say this is a coincidence: the reason why i started watching your videos was because i was struggling with this EXACT inequality which was assigned for my homework! Thank you very much for your help!

  • @MrAlex5452
    @MrAlex5452 5 ปีที่แล้ว +25

    I think you have a mistake at 6:29, when you expand the fractions. Shouldn't it be 2 - 1/c + 1/(c+1)^2 = 2 + (-1)/c + 1/(c+1)^2 = 2 + ((-(c+1)^2) + c)/(c(c+1)^2) = 2 - ((c+1)^2 - c)/(c(c+1)^2) ?

    • @srujanan
      @srujanan 20 วันที่ผ่านมา

      Yeah, there is a mistake with the signs that he took. My answer and yours match , but the video is still good none the less...

  • @namrashah4152
    @namrashah4152 5 ปีที่แล้ว +10

    I wasn't really able to do this by using (c+1)² - c instead of (c+1)² + c at 6:30 . Just changes the solution .

  • @LoLzWatsUsay
    @LoLzWatsUsay 11 ปีที่แล้ว +9

    At around 8:31 why are the terms subtracted instead?
    All you did was split the fraction up, so why does it have to be subtracted?

    • @LoLzWatsUsay
      @LoLzWatsUsay 11 ปีที่แล้ว

      ***** Ahhh I see
      Thanks Mr. Woo

  • @asimami3061
    @asimami3061 4 ปีที่แล้ว +5

    How you make a + to - in this question can you please explain.

  • @AwkwardFX
    @AwkwardFX 11 ปีที่แล้ว +5

    Induction Inequality Proof Example 1: Σ(k = 1 to n) 1/k² ≤ 2 - 1/n
    At time 5:44, how did you conjure up 2- (1/c+1) ? I mean, why do we have to specifically put it in that form? And how did you derive that expression?

    • @AwkwardFX
      @AwkwardFX 10 ปีที่แล้ว +2

      ***** Ah okay, I get it. I just wanna say, thanks for posting these videos. It helped me tremendously. I'm an undergrad in Comp Science and Discrete Math is such a torture.

  • @ievgenieris300
    @ievgenieris300 5 ปีที่แล้ว +4

    This is the best lesson for induction I've seen even though it is just about a single example

  • @AeanHD
    @AeanHD 10 ปีที่แล้ว +14

    6:28 is wrong with the signs

    • @shujamukhtar4563
      @shujamukhtar4563 4 ปีที่แล้ว

      he's correct. he did not multiply the signs as he's just working on the fraction independently.

  • @abobrhom7
    @abobrhom7 9 ปีที่แล้ว +9

    Why did you change the positive sign to negative sign ?? I think that is wrong !

    • @crawfordcarson134
      @crawfordcarson134 7 ปีที่แล้ว +3

      The negative (from subtracting) has to apply all parts of the fraction. It is correct.

    • @fillypenascimento198
      @fillypenascimento198 4 ปีที่แล้ว

      @@crawfordcarson134 Thank u so much, I was thinking that quarentine was blowing up my mind

  • @rosjohn5807
    @rosjohn5807 หลายเดือนก่อน

    At 8:43 , why did you change the fractions to subtraction instead of addition?

  • @faridabouabdallah9355
    @faridabouabdallah9355 6 ปีที่แล้ว +9

    Mistake with the sign at 6:29!! All wrong

  • @svetlanatemesheva2928
    @svetlanatemesheva2928 2 ปีที่แล้ว +1

    06:23, error, must be 2-\frac{(c+1)^2-c}{c(c+1)^2)}

  • @eftie33
    @eftie33 9 ปีที่แล้ว +4

    Sorry but why its minus? when you change it from a plus to a minus you have to change < to > and than its wrong

  • @specspec6851
    @specspec6851 8 หลายเดือนก่อน

    the only good explanation there is for this type of inductions

  • @adamikram3115
    @adamikram3115 2 ปีที่แล้ว +1

    I love you

  • @MyOneFiftiethOfADollar
    @MyOneFiftiethOfADollar 2 ปีที่แล้ว

    Nice induction proof. Not a very strong inequality since we know summation(n=1 to infinity) 1/n^2 is famously equal to PI^2/6 = 1.64. compare to n=30 where 2-1/30 = 59/30 greater than PI^2/6

  • @bradypinter8468
    @bradypinter8468 11 หลายเดือนก่อน

    Jesus Christ this man just saved my life

  • @DungeonHunter5awe
    @DungeonHunter5awe 9 ปีที่แล้ว +1

    if c is negative, it still works.

  • @syedalihasan309
    @syedalihasan309 ปีที่แล้ว

    I am stuck in a question of similar nature, could you please work it out for me..
    1/1^1/2 + 1/2^1/2+...+ 1/n^1/2 > or equal to (n+1)^1/2

  • @tinkageorgewilliam871
    @tinkageorgewilliam871 8 ปีที่แล้ว +1

    prove that if x and y are natural numbers such that k=(x^2 +y^2)/xy is an integer, then k=2

    • @TechToppers
      @TechToppers 4 ปีที่แล้ว +1

      Not going to use induction.
      x²/xy +y²/xy=k
      x/y + y/x =k
      x|y and y|x only possible when x=y(for integers). Plug this in.
      x/x +y/y = k
      1+1=k
      k=2😄

    • @tinkageorgewilliam871
      @tinkageorgewilliam871 4 ปีที่แล้ว

      @@TechToppers Hahah... Thanks. But you are 4 years late bro.

  • @simon1517
    @simon1517 6 ปีที่แล้ว

    This is really complicated! You can use a telescoping sum: Sum(k=1,n) 1/k^2

  • @TheJProducti0ns
    @TheJProducti0ns 4 ปีที่แล้ว +1

    Thank you!! The algebra was so mind bending on this one. I gave up after a while. Thank you for the video!

    • @TechToppers
      @TechToppers 4 ปีที่แล้ว

      Never give up! That's all.
      It feels unreal, but *Never give up* !

  • @felipefontenele648
    @felipefontenele648 3 ปีที่แล้ว

    Bro, its 10 PM and i need to send my activity at 11 PM and i get stuck on this fucking question. You are amazing men. Thanks men.

  • @reubenmanzo2054
    @reubenmanzo2054 2 ปีที่แล้ว

    In the 'Assume true for n=c' line, isn't it already given that c must be a positive integer, since c can only take the numbers that n can take?

  • @JoshY01
    @JoshY01 6 ปีที่แล้ว +1

    Thanks for the help! Better than my professor for sure!

  • @srabonratan1428
    @srabonratan1428 3 ปีที่แล้ว

    Prove that for all k ≤ n, pk(n) ≤ (n − k + 1)^k−1. Please someone solve it

  • @particleonazock2246
    @particleonazock2246 9 หลายเดือนก่อน

    thanks Yawei Hu

  • @isaacstrid2409
    @isaacstrid2409 2 ปีที่แล้ว

    I like it second last line 3

  • @tiin936
    @tiin936 2 ปีที่แล้ว

    thank u very much for making this vidd

  • @Banjara_Safar
    @Banjara_Safar 8 ปีที่แล้ว +1

    Thank you for the wonderful explanation ! :)

  • @rhettj
    @rhettj 2 ปีที่แล้ว

    Thank you, this was very helpful.

  • @timmoneel
    @timmoneel 5 ปีที่แล้ว

    Thank you for your proof! I am trying to help one of my family members to understand proof by induction. Your method was easy to follow. Thanks again!

  • @RC800
    @RC800 10 ปีที่แล้ว

    by the way thanks ....
    because of you I am clear with induction

  • @nabakumarmondal1859
    @nabakumarmondal1859 5 ปีที่แล้ว

    i want the proof of:
    1/2^2+1/3^2+1/4^2+...+1/n^2

    • @TechToppers
      @TechToppers 4 ปีที่แล้ว

      I've another cool method without induction. Wanna know that instead??

  • @MRussell798
    @MRussell798 7 ปีที่แล้ว

    there is a symbol for positive integer: N

  • @animeshyadav7486
    @animeshyadav7486 7 ปีที่แล้ว

    solve it again, it's wrong

  • @xxrawrgameremo98xx86
    @xxrawrgameremo98xx86 2 ปีที่แล้ว

    my hero :)

  • @PGN354
    @PGN354 3 ปีที่แล้ว

    Thank you ❤

  • @RathikMurtinty
    @RathikMurtinty ปีที่แล้ว +1

    For those saying this proof is incorrect, change the sign of c at 6:26 and work the proof out. The numerator will be c^2 + 2c + 1 - c which simplifies to c^2 + c + 1 = c(c+1) + 1. If you continue with the steps after you will get the same answer.

  • @panashemasimba4216
    @panashemasimba4216 3 ปีที่แล้ว

    This is beautiful

  • @RC800
    @RC800 10 ปีที่แล้ว +1

    ahhhhhhh founded 1st mistake in your video dude .....
    jzt a small sign difference make that sum wholly different ......

  • @pozzthanapat
    @pozzthanapat 9 ปีที่แล้ว

    very nice explanation

  • @mib141345
    @mib141345 11 ปีที่แล้ว

    Thank you so much! Really easy to follow :)

  • @serenasebastian6361
    @serenasebastian6361 7 ปีที่แล้ว +2

    6:29 wrong

  • @felipevega224
    @felipevega224 5 ปีที่แล้ว

    This is beatiful!

  • @shanethoney
    @shanethoney 10 ปีที่แล้ว

    Thank YOU!

  • @Jackstar923
    @Jackstar923 7 ปีที่แล้ว

    Thank you very much for the video, you saved my ass big time..