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Simplify the following expression:

[tex]\[ \log \left(9 x^5\right) + 5 \log \left(\frac{1}{x}\right) \][/tex]

A. [tex]\(\log 9\)[/tex]
B. [tex]\(\log 45\)[/tex]
C. [tex]\(\log 9 x^4\)[/tex]
D. [tex]\(\log 45 x^4\)[/tex]


Sagot :

To simplify the expression [tex]\(\log(9x^5) + 5 \log\left(\frac{1}{x}\right)\)[/tex], let's use the properties of logarithms step-by-step.

First, recall the logarithm properties:
1. [tex]\(\log(ab) = \log a + \log b\)[/tex]
2. [tex]\(\log\left(\frac{a}{b}\right) = \log a - \log b\)[/tex]
3. [tex]\(\log(a^b) = b \log a\)[/tex]

Given expression: [tex]\(\log(9x^5) + 5 \log\left(\frac{1}{x}\right)\)[/tex]

We will handle each part of the expression individually:

### Step 1: Simplify [tex]\(\log(9x^5)\)[/tex]

Using the property [tex]\(\log(ab) = \log a + \log b\)[/tex]:

[tex]\[ \log(9x^5) = \log 9 + \log x^5 \][/tex]

Then, using the property [tex]\(\log(a^b) = b \log a\)[/tex]:

[tex]\[ \log x^5 = 5 \log x \][/tex]

So,

[tex]\[ \log(9x^5) = \log 9 + 5 \log x \][/tex]

### Step 2: Simplify [tex]\(5 \log\left(\frac{1}{x}\right)\)[/tex]

Using the property [tex]\(\log \left(\frac{a}{b}\right) = \log a - \log b\)[/tex]:

[tex]\[ \log\left(\frac{1}{x}\right) = \log 1 - \log x \][/tex]

Since [tex]\(\log 1 = 0\)[/tex],

[tex]\[ \log\left(\frac{1}{x}\right) = -\log x \][/tex]

Then multiply by 5:

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

### Step 3: Combine the simplified parts

Now, combining the simplified parts from Step 1 and Step 2:

[tex]\[ \log(9x^5) + 5 \log\left(\frac{1}{x}\right) = (\log 9 + 5 \log x) + (-5 \log x) \][/tex]

Observe that [tex]\(5 \log x - 5 \log x\)[/tex] cancels out:

[tex]\[ \log(9x^5) + 5 \log\left(\frac{1}{x}\right) = \log 9 \][/tex]

### Conclusion:

Thus, the simplified form of [tex]\(\log(9x^5) + 5 \log\left(\frac{1}{x}\right)\)[/tex] is [tex]\(\log 9\)[/tex].

Hence, the correct answer is:

A. [tex]\(\log 9\)[/tex]