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Math Help - Two induction exercise

  1. #1
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    Two induction exercise

    Hi!

    Can anyone help me solcing these excercises please?

    a. Prove that 1*2+2*3+...+n(n+1)=[n(n+1)(n+2)]/3

    b. 1*2*3+2*3*4+...+n(n+1)(n+2)=?



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  2. #2
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    Re: Two induction exercise

    Quote Originally Posted by Kelvin88 View Post
    Can anyone help me solcing these excercises please?
    a. Prove that 1*2+2*3+...+n(n+1)=[n(n+1)(n+2)]/3
    b. 1*2*3+2*3*4+...+n(n+1)(n+2)=?
    What have you tried?
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  3. #3
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    Re: Two induction exercise

    There is a plan to follow for each proof by induction, and you don't have to think much to advance quite a bit. If you don't have anything better, you can find one description here. Or explain what exactly you don't understand. See also rule #11 in this sticky thread.
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  4. #4
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    Re: Two induction exercise

    Ok, i understand. I am sorry, actually these are from my homework (the easier ones), but have no idea how to start. Maybe at a. I should prove for P(1), then for P(n+1)? Then it will be 1*2+2*3+...+(n+1)(n+2) ?
    For b. I have no idea what should I do
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  5. #5
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    Re: Two induction exercise

    Quote Originally Posted by Kelvin88 View Post
    Maybe at a. I should prove for P(1), then for P(n+1)? Then it will be 1*2+2*3+...+(n+1)(n+2) ?
    Sort of, but please read how to do proofs by induction in your textbook, lecture notes, or the link above and follow that plan.
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