1)(a+b)^n - a^n - b^n is always divisible by ab for all n belongs to N.

2) a polynomial of odd degree will always have one of its roots to be either +1 or -1.

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## Comments

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TopNewestFor statement 1), use the binomial theorem to find that

\((a + b)^{n} = a^{n} + \binom{n}{1}a^{n-1}b + \binom{n}{2}a^{n-2}b^{2} + .... + \binom{n}{n-1}ab^{n-1} + b^{n}.\)

After subtracting \(a^{n}\) and \(b^{n}\) the remaining terms are all divisible by \(ab,\) and thus so is their sum.

Statement 2) is not actually true. \(f(x) = x - 2\) is of odd degree and only has root \(2.\)

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sir , I have a problem . I very much want to study number theory but I am unable to grasp the concepts beyond modular multiplication . I earnestly want to learn those Fermat rules ,Euler theorem , CRT etc,etc, Please help.

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Have you tried the wikis here on Brilliant.org? For example, here is the one on the CRT.

This can be found by choosing "Topics", followed by "Number Theory", "Modular Arithmetic" and then the 'open book' icon to the right of "Chinese Remainder Theorem". You can find the other topics in your list in this fashion as well.

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As for the "Started Problems" option, I noticed it missing from the main page a few days ago as well. I eventually found it, though. Click on the "blue planet" icon and choose the "View mobile site" option. Once on that page, click on the "three dot" icon in the upper right corner and you will see the "Started problems" option listed there. Then, if you want, you can choose the "View full site" option on the same list to take your list of started problems back to the main site format.

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