Question 269 of 480
Which of the following expressions is equivalent to \( (2^3 \times 2^{-5})^2 \) in standard form?
- \( 2^{-4} \)
- \( 2^{-2} \)
- \( 2^{-1} \)
- \( 2^{0} \)
Correct Answer:
B
Explanation
To solve the expression \( (2^3 \times 2^{-5})^2 \) and determine which of the given options is equivalent in standard form, we will break down the problem step-by-step.
### Step 1: Simplify the Expression Inside the Parentheses
The expression inside the parentheses is \( 2^3 \times 2^{-5} \). When multiplying powers with the same base, we can use the property of exponents that states:
\[
a^m \times a^n = a^{m+n}
\]
Applying this property here:
\[
2^3 \times 2^{-5} = 2^{3 + (-5)} = 2^{3 - 5} = 2^{-2}
\]
### Step 2: Raise the Result to the Power of 2
Now we need to raise the result \( 2^{-2} \) to the power of 2. Again, we use the property of exponents that states:
\[
(a^m)^n = a^{m \times n}
\]
So we have:
\[
(2^{-2})^2 = 2^{-2 \times 2} = 2^{-4}
\]
### Step 3: Identify the Correct Option
Now we have simplified the original expression to \( 2^{-4} \). We need to compare this with the options provided:
- A. \( 2^{-4} \)
- B. \( 2^{-2} \)
- C. \( 2^{-1} \)
- D. \( 2^{0} \)
The correct answer is **A. \( 2^{-4} \)**.
### Step 4: Explain Why Other Options Are Incorrect
- **Option B: \( 2^{-2} \)** - This is the result of the first step before raising it to the power of 2. It does not account for the squaring of \( 2^{-2} \), so it is incorrect.
- **Option C: \( 2^{-1} \)** - This is not related to our calculations at all. It does not represent any step in the simplification process and is therefore incorrect.
- **Option D: \( 2^{0} \)** - This represents the value of 1, which is not related to our expression. The expression \( 2^{-4} \) is not equal to \( 2^{0} \), making this option incorrect.
### Summary of Key Points
- We simplified \( 2^3 \times 2^{-5} \) to \( 2^{-2} \) using the property of exponents.
- We then raised \( 2^{-2} \) to the power of 2, resulting in \( 2^{-4} \).
- The correct answer is **A. \( 2^{-4} \)**, as it matches our final result.
- The other options do not correctly represent the simplification process or the final result.
### Revision Summary
- Use exponent rules: \( a^m \times a^n = a^{m+n} \) and \( (a^m)^n = a^{m \times n} \).
- Simplify expressions step-by-step to avoid mistakes.
- Always compare your final result with the provided options carefully.
- Remember that negative exponents indicate reciprocals, which can help in understanding the values.