#17 proof prove induction 8^n-1 is divisible by 7 divides mathgotserved induccion

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Why not use the following for the induction step? Assume by induction hypothesis that 8^n - 1 is divisible by 7. We need to establish that 8^(n+1) - 1 is divisible by 7.
8^(n+1) - 1 = 8*8^n - 1 = 7 * (8^n - 1) + (8^n - 1)
Now 7 * (8^n - 1) is divisible by 7 and (8^n - 1) is divisible by 7 by the induction hypothesis so their sum is also divisible by 7.

This proof is much simpler if you ask me since you do not have to worry about the formal definition of 'divisibility' and hence not have to worry about the integer m.

Crbneum
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Great work on divisibility and induction. Keep it up woo hoo 

mathsgotserved
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Waoooo 👌👌👌sir I'm so impressed your way of teaching👍👍👍 I'm from Pakistan

enayahkhan
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Thank you so much
Your explanation was very clear and helpful to me!!

oyohval
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I had a little trouble understanding that 7(8m+1), but finally got it, xd. Basically, we want to prove that the formula is multiple of 7. So If all equation 8m+1 is multiplying by 7 it mandatory means that its multiple:3 We don't want to prove that the formula has all multiples of 7 though, that's why I wasn't getting it, at the start.

YvtqKn
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thanks very much for the videos/lectures . with this, you motivate the spirit of mathematics in up growing mathematicians

enowjordan
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Thank you so much it saved me in my exam

PeachIsLive
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I have a question which is
(3+√5) ^n + (3- √5)^n

michaelcoker
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I'm from Brazil!! thanks you was help me much!!

grazielauzumaki
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Can you solve
where n is any positive odd integer
Plz do it

RameshSharma-zgwx
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please do a video of the question👉3^2n+1 + 2^2n+1 is divisible by 7

priyankachakraborty
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6:25 why is it equals to 7m? pls reply pls

Wendychin
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if the bases are the same .then why dont subtract the '1' from both bases?

kdtode
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Well of course 7 | 8^n - 1 because k | (k + 1)^n - 1 for natural numbers k and n.

georgemissailidis
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make a vedio on 7^n-3^n is divisible by 4

abduljabbar-mbpk
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This is a question from my leaving cert maths paper

gracekim
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Waoooo 👌👌👌sir I'm so impressed your way of teaching👍👍👍 I'm from Pakistan

enayahkhan