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Further maths help - proof by induction (divisibility)

I need help on what to do next :smile:
Original post by kurmancii_
I need help on what to do next :smile:


Ok so notice that from your last line you can say:

10(11k+1)+143(122k1)=10(11k+1)+10(122k1)+133(122k1)10(11^{k+1}) + 143(12^{2k-1}) = 10(11^{k+1}) + 10(12^{2k-1}) + 133(12^{2k-1}).

What do you notice from here??
Original post by RDKGames
Ok so notice that from your last line you can say:

10(11k+1)+143(122k1)=10(11k+1)+10(122k1)+133(122k1)10(11^{k+1}) + 143(12^{2k-1}) = 10(11^{k+1}) + 10(12^{2k-1}) + 133(12^{2k-1}).

What do you notice from here??


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Original post by 3pointonefour

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Original post by RDKGames

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Original post by 3pointonefour

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(edited 5 years ago)
Reply 6
Original post by RDKGames

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Ok so 10 was a common factor so i factored it out.
After that, i needed to add f(k) after to the equation, which i did. I looked blankly at my paper when i realised that 10(11^k+1 + 12^2k-1) is equal to the assumtion step equation thingy. Therefore, i got 10f(k) + f(k) + 133(12^2k-1). I think im done?? my final answer is there on the paper
Reply 7
Original post by kurmancii_
Ok so 10 was a common factor so i factored it out.
After that, i needed to add f(k) after to the equation, which i did. I looked blankly at my paper when i realised that 10(11^k+1 + 12^2k-1) is equal to the assumtion step equation thingy. Therefore, i got 10f(k) + f(k) + 133(12^2k-1). I think im done?? my final answer is there on the paper


Yeah heres the pic
Original post by kurmancii_
Yeah heres the pic


Yes you are done with the algebra and whatnot. You just need a closing statement to complete the proof.
Reply 9
Original post by RDKGames
Yes you are done with the algebra and whatnot. You just need a closing statement to complete the proof.


The closing statement is so damn flipping long. How am i meant to remember the statement for normal induction and divisibility induction? It's like revising for gcse english quotes lol
Original post by kurmancii_
The closing statement is so damn flipping long. How am i meant to remember the statement for normal induction and divisibility induction? It's like revising for gcse english quotes lol


It doesn't take that long.

"133f(k)133|f(k) by assumption, hence 133(11f(k)+133(122k1))    133f(k+1)133|(11f(k)+133(12^{2k-1})) \implies 133|f(k+1). Hence 133f(n)133|f(n) for all nNn \in \mathbb{N} by the principle of mathematical induction."
(edited 5 years ago)

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