Chapter 12 Sequences and Series - 12.3 Analyze Geometric Sequences and Series - 12.3 Exercises - Skill Practice - Page 814: 31

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The sequence is geometric with first term $a_2=15$ and common ratio $r=\frac{1}{2}$. So, a rule for the nth term is:$$a_n=a_2r^{n-2}=15.(\frac{1}{2})^{n-2}=30\times(\frac{1}{2})^{n-1}$$ The first 6 terms are $a_1=30\\a_2=15\\a_3=7.5\\a_4=3.75\\a_5=1.875\\a_6=0.9375$