To find the value of \( \log_7(5.1) \) using the change of base formula, we can use:
\[ \log_b(a) = \frac{\log_k(a)}{\log_k(b)} \]
where \( k \) can be any positive number (commonly, we use 10 or e). We will use base 10 for our calculation:
\[ \log_7(5.1) = \frac{\log_{10}(5.1)}{\log_{10}(7)} \]
Now let's calculate the logarithms:
- Calculate \( \log_{10}(5.1) \):
Using a calculator: \[ \log_{10}(5.1) \approx 0.70757 \]
- Calculate \( \log_{10}(7) \):
Using a calculator: \[ \log_{10}(7) \approx 0.84510 \]
Now, we substitute these values into the change of base formula:
\[ \log_7(5.1) \approx \frac{0.70757}{0.84510} \approx 0.837 \]
Thus, the value of \( \log_7(5.1) \) to the nearest thousandth is approximately:
\[ \boxed{0.837} \]