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Induction: Prove that $4^{n+1}+5^{2 n - 1}$ is divisible by 21 for all $n \geq 1$.

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    Do you have to use induction - it can be done without.2012-11-02
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    Hint: $25 = 4 + 21$2012-11-02
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    What is your base case? Is the assertion true for $n=1$? Then proceed with your inductive hypothesis (assume true for n)...then show it is true for n+1.2012-11-02
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    Great, it looks like everyone has pretty much done the OP's homework... :-/2012-11-02

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