\( \sum _ { p = 0 } ^ { m } 3 ( 2 ) ^ { 2 p - 3 } < 8000 \)
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The Deep Dive
To solve the inequality \( \sum _ { p = 0 } ^ { m } 3 ( 2 ) ^ { 2 p - 3 } < 8000 \), we first recognize the series as a geometric series. The general term can be simplified to \( 3 \cdot 2^{2p-3} = \frac{3}{8} \cdot (2^2)^p = \frac{3}{8} \cdot 4^p \). The sum of the series can be computed as follows: \[ \sum_{p=0}^{m} 3(2)^{2p - 3} = \frac{3}{8} \sum_{p=0}^{m} 4^p \] The sum of a geometric series \( \sum_{p=0}^{m} r^p \) is given by \( S = \frac{r^{m + 1} - 1}{r - 1} \). Here, \( r = 4 \): \[ \sum_{p=0}^{m} 4^p = \frac{4^{m + 1} - 1}{4 - 1} = \frac{4^{m + 1} - 1}{3} \] Substituting back, we have: \[ \sum_{p=0}^{m} 3(2)^{2p - 3} = \frac{3}{8} \cdot \frac{4^{m + 1} - 1}{3} = \frac{4^{m + 1} - 1}{8} \] Now, we can set up our inequality: \[ \frac{4^{m + 1} - 1}{8} < 8000 \] Multiplying both sides by 8 gives: \[ 4^{m + 1} - 1 < 64000 \] Adding 1: \[ 4^{m + 1} < 64001 \] To solve for \( m \), we take logarithms: \[ m + 1 < \log_4(64001) \] Since \( \log_4(64001) = \frac{\log_{10}(64001)}{\log_{10}(4)}\). Calculating \( \log_{10}(64001) \approx 4.806 \) and \( \log_{10}(4) \approx 0.602 \): \[ \log_4(64001) \approx \frac{4.806}{0.602} \approx 7.98 \] Thus, \[ m + 1 < 7.98 \quad \Rightarrow \quad m < 6.98 \] This means the largest integer \( m \) is 6. To summarize, the maximum value of \( m \) that satisfies the original inequality is 6.