Chapter 12 Sequences and Series - 12.3 Analyze Geometric Sequences and Series - 12.3 Exercises - Skill Practice - Page 814: 36

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The sequence is geometric with first term $a_4=500$ and common ratio $r=5$. We obtain: $$a_n=a_4r^{n-4}\\a_n=500\times5^{n-4}\\a_n=4\times5^{n-1}$$ The first 6 terms are $a_1=4\\a_2=20\\a_3=100\\a_4=500\\a_5=2500\\a_6=12500$