In this case, the first term $a_1$ is the initial value of the car, which is $\$64,000$. The common ratio $r$ is the rate of depreciation each year, which is $1 - 0.15 = 0.85$. So, the general term of the sequence is
\[a_n = 64000 \cdot 0.85^{(n-1)}.\]
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