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Prove $a\cdot (10)^n\equiv a\cdot 1\pmod 3$ using induction.

I need to prove this equation to be true not sure how to solve. I know I have to first use one and then plug in $k+1$ but what am I plugging it into a or n and then how do I solve?

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  • $\begingroup$ Do you have to use induction? $\endgroup$ – user258700 Dec 3 '15 at 16:19
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    $\begingroup$ The solution without induction is much simpler since $10\equiv 1\pmod{3}$. $\endgroup$ – Jack Frost Dec 3 '15 at 16:27
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$$a\cdot 10^k \equiv a \quad(mod3)$$ $$a\cdot 10^{k+1}=a\cdot 10^k\cdot (9+1)\equiv a\cdot 10^k \equiv a \quad(mod3)$$

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