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# Prove it

Prove that $$2^{4m}-1$$ is divisible by 15,where $$m$$ is any integer.

Note by Ravi Ranjan
2 years, 1 month ago

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2^4 = 1 (mod 15) or, 2^4m = 1 (mod 15) or, 2^4m -1 = 0 (mod 15)

And it's proved.

- 2 years ago

Put m=1 2^4=16 16-1=15 15 is divisible on 15... Answer is yes......(2^4m)-1 is divisible on 15.....

- 2 years, 1 month ago

You did not prove it, you just checked a case. Checking a case that does not represent all other cases is not a proof.

- 2 years ago