AoPS Wiki:Problem of the Day/July 8, 2011

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Revision as of 19:05, 7 July 2011 by Btilm305 (talk | contribs) (new problem)
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What is the coefficient of $a^{-1/2}$ in the expansion of $\left(a-\frac{1}{\sqrt{a}}\right)^7$?