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Use the change of base formula to evaluate the logarithms to the nearest thousandth.

Change of base formula:
[tex]\[ \log _a x=\frac{\log _b x}{\log _b a} \][/tex]

Evaluate the following:

[tex]\[
\begin{array}{l}
\log _3 6=\square \\
\log _5 20=\square \\
\log _2\left(\frac{1}{5}\right)=\square
\end{array}
\][/tex]

Sagot :

To evaluate the given logarithms, we will use the change of base formula:

[tex]\[ \log_a x = \frac{\log_b x}{\log_b a} \][/tex]

where [tex]\( \log_b \)[/tex] denotes the logarithm with base [tex]\( b \)[/tex]. We will use the natural logarithm (base [tex]\( e \)[/tex]) for convenience.

### 1. Evaluating [tex]\( \log_3 6 \)[/tex]:

Using the change of base formula, we get:

[tex]\[ \log_3 6 = \frac{\log 6}{\log 3} \][/tex]

Note that [tex]\( \log \)[/tex] denotes the natural logarithm here.

The result of calculating [tex]\( \log_3 6 \)[/tex] rounded to the nearest thousandth is:

[tex]\[ \log_3 6 \approx 1.631 \][/tex]

### 2. Evaluating [tex]\( \log_5 20 \)[/tex]:

Similarly, using the change of base formula, we get:

[tex]\[ \log_5 20 = \frac{\log 20}{\log 5} \][/tex]

The result of calculating [tex]\( \log_5 20 \)[/tex] rounded to the nearest thousandth is:

[tex]\[ \log_5 20 \approx 1.861 \][/tex]

### 3. Evaluating [tex]\( \log_2 \left( \frac{1}{5} \right) \)[/tex]:

Again, using the change of base formula, we have:

[tex]\[ \log_2 \left( \frac{1}{5} \right) = \frac{\log \left( \frac{1}{5} \right)}{\log 2} \][/tex]

Since [tex]\( \frac{1}{5} \)[/tex] is a fraction, its logarithm is negative. The result of calculating [tex]\( \log_2 \left( \frac{1}{5} \right) \)[/tex] rounded to the nearest thousandth is:

[tex]\[ \log_2 \left( \frac{1}{5} \right) \approx -2.322 \][/tex]

Summarizing, the evaluated logarithms are:
[tex]\[ \begin{array}{l} \log_3 6 \approx 1.631 \\ \log_5 20 \approx 1.861 \\ \log_2 \left( \frac{1}{5} \right) \approx -2.322 \end{array} \][/tex]