 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2019/paper-1/7/b/solution

This is a finite geometric series with first term and common ratio both equal to four. Therefore

n = 1 \sum 5 4^{n} = \frac{4 ( 4 ^{5} - 1 )}{4 - 1} = 1364.

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