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Question
Evaluate the following:
\[\sum^{10}_{n = 2} 4^n\]
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Solution
\[\sum^{10}_{n = 2} 4^n = 4^2 + 4^3 + 4^4 + . . . + 4^{10} \]
\[ = 16 + 64 + 256 + . . . + 4^{10} \]
\[ = 16\left( \frac{4^9 - 1}{4 - 1} \right) = \frac{16}{3}\left( 4^9 - 1 \right)\]
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