Induction: Divisibility Proof example 5 (8^n+2(7^n)-1 has a factor of 7)

Since 2*7^n is always divisible by 7 anyway, you could take a shortcut that is not related to induction and instead prove that 8^n-1 is divisible by 7. And that is quite a bit shorter:
8^1-1=8-1=7

[tofiquehayat]

thank you im learning this for further mathematics in the united kingdom, and this was the hardest topic, but i now i do get it

[harunlisic]

Did he make a mistake or 2(7*7^k)=14*7^k. I thought you multiply every element inside the parentheses with 2.

[diyakshitha]

Thanks a lot for this video it really helped me