What is the solution to the equation below?

[tex]\[ \log (20 x^3) - 2 \log x = 4 \][/tex]

A. [tex]\( x = 25 \)[/tex]

B. [tex]\( x = 50 \)[/tex]

C. [tex]\( x = 250 \)[/tex]

D. [tex]\( x = 500 \)[/tex]



Answer :

To solve the given equation
[tex]\[ \log (20x^3) - 2 \log (x) = 4, \][/tex]
we will use the properties of logarithms to simplify and solve for [tex]\(x\)[/tex].

### Step 1: Use the property of logarithms:

First, recall the logarithm property:
[tex]\[ \log (a \cdot b) = \log a + \log b. \][/tex]
Applying this property to [tex]\(\log (20x^3)\)[/tex], we get:
[tex]\[ \log (20x^3) = \log 20 + \log x^3. \][/tex]

### Step 2: Simplify [tex]\(\log x^3\)[/tex]:

Using another property of logarithms,
[tex]\[ \log x^3 = 3\log x, \][/tex]
we rewrite the equation as:
[tex]\[ \log 20 + 3\log x - 2\log x = 4. \][/tex]

### Step 3: Combine like terms:

Combine the logarithmic terms involving [tex]\(x\)[/tex]:
[tex]\[ \log 20 + 3\log x - 2 \log x = \log 20 + \log x = 4. \][/tex]

### Step 4: Use the property of logarithms again:

Using the property that [tex]\(\log a + \log b = \log (ab)\)[/tex], we have:
[tex]\[ \log (20x) = 4. \][/tex]

### Step 5: Convert from logarithmic form to exponential form:

Recall that [tex]\(\log a = b \implies 10^b = a\)[/tex]. So,
[tex]\[ 20x = 10^4. \][/tex]

Evaluate [tex]\(10^4\)[/tex]:
[tex]\[ 10^4 = 10000. \][/tex]

Thus,
[tex]\[ 20x = 10000. \][/tex]

### Step 6: Solve for [tex]\(x\)[/tex]:

Divide both sides by 20 to solve for [tex]\(x\)[/tex]:
[tex]\[ x = \frac{10000}{20} = 500. \][/tex]

### Conclusion:

The value of [tex]\(x\)[/tex] that satisfies the equation
[tex]\[ \log (20x^3) - 2 \log (x) = 4 \][/tex]
is [tex]\(x = 500\)[/tex].

Thus, the correct answer is:
[tex]\[ \boxed{500}. \][/tex]