Answer
$-200$
Work Step by Step
The nth term can be obtained by $a_n=a_1\cdot r^{n-1}$ where $a_1$ is the first term and $r$ is the common ratio.
Hence here: $a_6=6400\cdot(\frac{-1}{2})^5=6400\cdot\frac{-1}{32}=-200$
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