Mathematical Induction - Proof of ∑r=n(n+1)/2 | ExamSolutions

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  • Опубліковано 12 січ 2025

КОМЕНТАРІ • 18

  • @cipherunity
    @cipherunity 9 років тому +26

    There is a simple solution of this problem for those who are not aware of mathematical induction.
    Let S1 = 1 + 2 + 3 + . . . +(n-2)+(n-1)+(n)
    We can also write by re-arranging
    S1 = (n) + (n-1) + (n-2)+ . . . + 3 + 2 + 1
    Adding both equations
    2S1 = (n+1) + (n+1) +( n+1) + . . . +(n+1) + (n+1) + (n+1) n terms
    2S1 = n (n+1)
    Hence S1 = n (n+1)/2
    Show less

    • @iDontcare_000
      @iDontcare_000 7 років тому +3

      This is not mathematical induction, this is the proof by series rather than the whole n=1, n=k, n=k+1 method or method of differences. I wouldn't recommend doing it this way, because its not on the mark scheme. Although it might be a creditable method I'd rather not take my chances on FP1.

    • @topaussiemezza5715
      @topaussiemezza5715 7 років тому +1

      It's better just to learn it the way he has shown it. There are alternative proofs to lots of things in mathematics; but, in general; it's worth knowing induction (broad technique) over those alternatives (usually less intuitive than induction). I've done enough tests involving proofs to know that induction is expected over and over, again.

    • @topaussiemezza5715
      @topaussiemezza5715 7 років тому +1

      Also, a lot of alternative proofs look like one-offs that suit for the particular scenario to be proven. Induction is broad and I've seen it used over and over in graph theory, alone. I used to dislike induction; but, it ends up feeling really easy, formulaic and intuitive.

  • @ExamSolutions_Maths
    @ExamSolutions_Maths  12 років тому +10

    That was quick!

  • @chidochiradza
    @chidochiradza 11 місяців тому +4

    my exam is in an hour 30 and i just found this precious video which just saved my life

  • @EddieBlundell
    @EddieBlundell 12 років тому +1

    Thankyou! The last bit helped things click for me, I'm using proof by induction whilst studying recursion. As it's true for the base case, and we've proved it's true for k+1, we know it's true for 2 and so on.

  • @topaussiemezza5715
    @topaussiemezza5715 7 років тому +1

    I watched your induction videos a number of months ago & I gotta say they're basically the best I've ever fucking seen on UA-cam. Helped me to like induction & see how easy it actually is. Sarada Herke does good proofs in graph theory, too. Other uploaders I've seen are just overrated & don't even cover different induction scenarios like these videos.

  • @ExamSolutions_Maths
    @ExamSolutions_Maths  11 років тому +2

    Good to hear

  • @cosmickitty9533
    @cosmickitty9533 8 років тому +1

    wonderful thank you!

  • @benzola4808
    @benzola4808 11 років тому +1

    i bet you won't get a better explanation than this....

  • @fireyonghan
    @fireyonghan 12 років тому

    Thank you. Gotta be flexible and embrace the dots.

  • @AbrhamAbiye
    @AbrhamAbiye 8 місяців тому +1

    Thanks

  • @eliseratcliffe2729
    @eliseratcliffe2729 11 років тому +1

    I love maths

  • @davellew69
    @davellew69 12 років тому +4

    I`m relly sorry but you have confused me even more

  • @ExamSolutions_Maths
    @ExamSolutions_Maths  12 років тому

    Oh dear!