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

(a) [tex]\log_5 45 - 2 \log_5 3 = \square[/tex]

(b) [tex]\ln e^{-9} + \ln e^5 = \square[/tex]



Answer :

Sure! Let's solve each part step-by-step using properties of logarithms.

### Part (a)
Evaluate [tex]\(\log_5 45 - 2 \log_5 3\)[/tex]:

1. Use the property of logarithms which states [tex]\(a \log_b(x) = \log_b(x^a)\)[/tex]:
[tex]\[ 2 \log_5 3 = \log_5 (3^2) \][/tex]
Simplify [tex]\(3^2\)[/tex]:
[tex]\[ \log_5 9 \][/tex]

2. Substitute [tex]\(\log_5 9\)[/tex] back into the original expression:
[tex]\[ \log_5 45 - \log_5 9 \][/tex]

3. Use the logarithmic property [tex]\(\log_b(x) - \log_b(y) = \log_b\left(\frac{x}{y}\right)\)[/tex]:
[tex]\[ \log_5 \left(\frac{45}{9}\right) \][/tex]

4. Simplify [tex]\(\frac{45}{9}\)[/tex]:
[tex]\[ \log_5 5 \][/tex]

5. Since [tex]\(\log_5 5\)[/tex] is the logarithm of 5 base 5, it simplifies to:
[tex]\[ 1 \][/tex]

So the solution to (a) is:

[tex]\[ \log_5 45 - 2 \log_5 3 = 1 \][/tex]

### Part (b)
Evaluate [tex]\(\ln e^{-9} + \ln e^5\)[/tex]:

1. Use the property [tex]\(\ln(e^x) = x\)[/tex]:
[tex]\[ \ln e^{-9} = -9 \quad \text{and} \quad \ln e^5 = 5 \][/tex]

2. Substitute these values back into the expression:
[tex]\[ -9 + 5 \][/tex]

3. Perform the addition:
[tex]\[ -4 \][/tex]

So the solution to (b) is:

[tex]\[ \ln e^{-9} + \ln e^5 = -4 \][/tex]

Combining the results, we have:

(a) [tex]\(\log_5 45 - 2 \log_5 3 = 1\)[/tex]

(b) [tex]\(\ln e^{-9} + \ln e^5 = -4\)[/tex]