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Evaluate the given expressions. $$8^{-1 / 3}$$

Short Answer

Expert verified
The evaluation of \( 8^{-1/3} \) is \( \frac{1}{2} \).

Step by step solution

01

Understand Negative Exponents

When you see a negative exponent, it indicates a reciprocal. Specifically, \( a^{-b} = \frac{1}{a^b} \). Therefore, for \( 8^{-1/3} \), we can rewrite it as \( \frac{1}{8^{1/3}} \).
02

Understand Fractional Exponents

Fractional exponents correspond to roots. The expression \( a^{1/b} \) is equivalent to \( \sqrt[b]{a} \). Thus, \( 8^{1/3} \) means the cube root of 8. So, we need \( \frac{1}{\sqrt[3]{8}} \).
03

Calculate the Cube Root

Find the cube root of 8. The cube root of a number is a value that, when multiplied by itself three times, gives the original number. Since \( 2 \times 2 \times 2 = 8 \), the cube root of 8 is 2. Thus, \( \sqrt[3]{8} = 2 \).
04

Apply Reciprocal to Cube Root

Inserting the value from the previous step, \( \frac{1}{\sqrt[3]{8}} \) becomes \( \frac{1}{2} \). Therefore, \( 8^{-1/3} = \frac{1}{2} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Fractional Exponents
Fractional exponents may seem intimidating at first, but they actually provide a clear and compact way to express roots in mathematics.
When you encounter an expression like \( a^{1/n} \), you can interpret it as the \( n^{th} \) root of \( a \). For example, \( a^{1/2} \) is the square root of \( a \), and similarly, \( a^{1/3} \) signifies the cube root. Here’s why it makes sense:
  • The numerator of the fraction indicates the power to which you raise the base.
  • The denominator points to the type of root.
Consider the expression \( 8^{1/3} \). This is equivalent to calculating the cube root of 8. You will learn that it breaks down the calculation into manageable steps, making complex roots approachable.
Reciprocal
The concept of a reciprocal is straightforward: it simply involves flipping a number over.
Mathematically, the reciprocal of a number \( a \) is \( \frac{1}{a} \). When a number includes a negative exponent like \( a^{-b} \), it implies taking the reciprocal of \( a^b \).
To visualize this, if you have \( 8^{-1/3} \), you start by finding \( 8^{1/3} \) first, and then take its reciprocal. Hence, it becomes \( \frac{1}{8^{1/3}} \). This strategy simplifies the handling of negative exponents and brings more clarity to calculations. You may find it helpful to remember that each negative exponent can guide you into making a fraction.
Cube Root
Finding cube roots is essential when dealing with fractional exponents, particularly of the form \( a^{1/3} \).
The cube root of a number \( a \) is a number \( b \) such that \( b \times b \times b = a \).
This process is rooted in understanding that you’re essentially looking for a number which, taken as the factor three times, reconstructs the original number.
For instance, with the expression \( 8^{1/3} \), you are seeking a value that, when multiplied by itself twice, results in 8. As shown in the step-by-step solution, since \( 2 \times 2 \times 2 = 8 \), the cube root of 8 is 2. Recognizing this pattern can help you approach any mathematical problem involving cube roots with confidence.

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