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Use the properties of logarithms to evaluate each of the following expressions.

(a) [tex]2 \log_6 2 + \log_6 9[/tex]

(b) [tex]\ln e^3 - \ln e^{13}[/tex]


Sagot :

Sure, let's break down each expression using properties of logarithms step-by-step:

### Part (a)

Expression: [tex]\( 2 \log_6(2) + \log_6(9) \)[/tex]

1. Apply the power rule of logarithms: The power rule states [tex]\( a \log_b(c) = \log_b(c^a) \)[/tex]. Applying this to [tex]\( 2 \log_6(2) \)[/tex]:

[tex]\[ 2 \log_6(2) = \log_6(2^2) = \log_6(4) \][/tex]

2. Combining the logarithms: Logarithms can be added together using the product rule, which states [tex]\( \log_b(a) + \log_b(c) = \log_b(ac) \)[/tex]. We apply this to our current expression:

[tex]\[ \log_6(4) + \log_6(9) = \log_6(4 \times 9) = \log_6(36) \][/tex]

3. Evaluate the logarithm: We now have [tex]\( \log_6(36) \)[/tex]. Since [tex]\( 6^2 = 36 \)[/tex], we know:

[tex]\[ \log_6(36) = 2 \][/tex]

Therefore, [tex]\( 2 \log_6(2) + \log_6(9) = 2 \)[/tex].

### Part (b)

Expression: [tex]\( \ln(e^3) - \ln(e^{13}) \)[/tex]

1. Apply the power rule for natural logarithms: The power rule states [tex]\( \ln(a^b) = b \ln(a) \)[/tex]. Applying this to both terms:

[tex]\[ \ln(e^3) = 3 \ln(e) \quad \text{and} \quad \ln(e^{13}) = 13 \ln(e) \][/tex]

2. Simplify using properties of natural logarithms: Since the natural logarithm of [tex]\( e \)[/tex], [tex]\( \ln(e) \)[/tex], equals 1, we simplify:

[tex]\[ \ln(e) = 1 \][/tex]

So,

[tex]\[ 3 \ln(e) = 3 \times 1 = 3 \quad \text{and} \quad 13 \ln(e) = 13 \times 1 = 13 \][/tex]

3. Combine the results: Subtract the two results:

[tex]\[ 3 - 13 = -10 \][/tex]

Therefore, [tex]\( \ln(e^3) - \ln(e^{13}) = -10 \)[/tex].

In summary:
- For (a), [tex]\( 2 \log_6(2) + \log_6(9) = 2 \)[/tex]
- For (b), [tex]\( \ln(e^3) - \ln(e^{13}) = -10 \)[/tex]