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[tex]a. r^{4}=162 \\ a. r^{2}=18 \\ ------: \\ r^{2}=9 \\ r=3 \\ a. 3^{2}=18 \\ a.9=18 \\ a=2 \\ U9=a. r^{9-1} \\ U9= 2. 3^{8} \\ U9= 13122 (A) [/tex]

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