Amarante
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Hi, I was practising proof by induction and came across this question (9b june 2014 IAL) which I think I've correctly proved. However, the mark scheme doesn't show my method among the alternatives so I was wondering if I would still get the marks. I skipped basis case and conclusion for timing purposes. Can someone verify whether this method is correct or not?
Thanks in advance
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RDKGames
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(Original post by Amarante)
Hi, I was practising proof by induction and came across this question (9b june 2014 IAL) which I think I've correctly proved. However, the mark scheme doesn't show my method among the alternatives so I was wondering if I would still get the marks. I skipped basis case and conclusion for timing purposes. Can someone verify whether this method is correct or not?
Thanks in advance

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Looks fine though generally you need make use of the fact that 4^k+6k+8 is divisible by 18 directly, not its rearrangement - exam boards could be picky on that, not sure.
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_gcx
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(Original post by Amarante)
Hi, I was practising proof by induction and came across this question (9b june 2014 IAL) which I think I've correctly proved. However, the mark scheme doesn't show my method among the alternatives so I was wondering if I would still get the marks. I skipped basis case and conclusion for timing purposes. Can someone verify whether this method is correct or not?
Thanks in advance
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Views: 54
Size:  79.6 KB


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That looks fine, although in general it's probably safer, to use f(k+1) = f(k) + g(k), where g(k) = f(k+1)-f(k), proving that g(k) is divisible by 18, and making deductions accordingly.
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Amarante
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(Original post by _gcx)
That looks fine, although in general it's probably safer, to use f(k+1) = f(k) + g(k), where g(k) = f(k+1)-f(k), proving that g(k) is divisible by 18, and making deductions accordingly.
(Original post by RDKGames)
Looks fine though generally you need make use of the fact that 4^k+6k+8 is divisible by 18 directly, not its rearrangement - exam boards could be picky on that, not sure.
Thank you very much, I'll stick to the safer option


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