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1990 AHSME Problems/Problem 30

Revision as of 21:58, 18 February 2012 by Ckorr2003 (talk | contribs) (Created page with "Let <math>R_n=\frac{1}{2}(a^n+b^n)</math> for each non-negative integer <math>n</math> where <math>a=3+2\sqrt{2}</math> and <math>b=3-2\sqrt{2}</math>. The value of <math>R_{1234...")
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Let $R_n=\frac{1}{2}(a^n+b^n)$ for each non-negative integer $n$ where $a=3+2\sqrt{2}$ and $b=3-2\sqrt{2}$. The value of $R_{12345}$ is an integer. What is its units digit?

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