Question 166 of 480
If \(\frac{9^{2x-1}}{27^{x+1}} = 1\), find the value of x.
Correct Answer:
B
Explanation
To solve the equation \(\frac{9^{2x-1}}{27^{x+1}} = 1\), we will first rewrite the bases in terms of powers of 3, since both 9 and 27 can be expressed as powers of 3.
### Step 1: Rewrite the bases
- We know that \(9 = 3^2\) and \(27 = 3^3\).
- Therefore, we can rewrite the equation as follows:
\[
\frac{(3^2)^{2x-1}}{(3^3)^{x+1}} = 1
\]
### Step 2: Simplify the expression
Using the power of a power property \((a^m)^n = a^{m \cdot n}\), we can simplify the numerator and the denominator:
\[
\frac{3^{2(2x-1)}}{3^{3(x+1)}} = 1
\]
This simplifies to:
\[
\frac{3^{4x-2}}{3^{3x+3}} = 1
\]
### Step 3: Apply the quotient rule for exponents
Using the quotient rule for exponents, which states that \(\frac{a^m}{a^n} = a^{m-n}\), we can further simplify:
\[
3^{(4x-2) - (3x+3)} = 1
\]
This simplifies to:
\[
3^{4x - 2 - 3x - 3} = 1
\]
### Step 4: Combine like terms
Now, combine the terms in the exponent:
\[
3^{(4x - 3x) - (2 + 3)} = 3^{x - 5} = 1
\]
### Step 5: Solve for the exponent
We know that \(3^0 = 1\). Therefore, we can set the exponent equal to zero:
\[
x - 5 = 0
\]
### Step 6: Solve for \(x\)
Now, solve for \(x\):
\[
x = 5
\]
### Conclusion
Thus, the value of \(x\) is \(5\).
### Explanation of Options
- **Option A (8)**: This is incorrect because substituting \(x = 8\) into the original equation does not satisfy it.
- **Option B (5)**: This is correct as we have shown through our calculations that \(x = 5\) satisfies the equation.
- **Option C (3)**: This is incorrect for the same reason as option A; substituting \(x = 3\) does not satisfy the original equation.
- **Option D (2)**: This is also incorrect; substituting \(x = 2\) does not satisfy the original equation.
### Revision Summary
- Rewrite bases in terms of a common base (in this case, powers of 3).
- Use properties of exponents to simplify the equation.
- Set the exponent equal to zero when the expression equals 1.
- Solve for the variable to find the correct answer.
The correct answer is **B. 5**.