Chapter 0: Problem 15
Evaluate each expression. (a) \(\left(\frac{1}{32}\right)^{2 / 5}\) (b) \((27)^{-4 / 3}\) (c) \(\left(\frac{1}{8}\right)^{-2 / 3}\)
Short Answer
Expert verified
(a) \(\frac{1}{4}\), (b) \(\frac{1}{81}\), (c) \(4\)
Step by step solution
01
Expression (a) Simplify the Base
For the expression \(\left(\frac{1}{32}\right)^{2/5}\), first note that \(32 = 2^5\). Consequently, \(\frac{1}{32} = 2^{-5}\). So, the expression simplifies to \((2^{-5})^{2/5}\).
02
Apply the Power of a Power Rule in (a)
Use the rule \((a^m)^n = a^{m \cdot n}\) to simplify \((2^{-5})^{2/5}\) as follows: \((2^{-5})^{2/5} = 2^{-5 \times 2/5} = 2^{-2}\).
03
Evaluate (a) to a Simplified Form
Now calculate \(2^{-2}\): This is \(\frac{1}{2^2} = \frac{1}{4}\). So, the value of \(\left(\frac{1}{32}\right)^{2/5}\) is \(\frac{1}{4}\).
04
Expression (b) Simplify the Base
For \((27)^{-4/3}\), recognize that \(27 = 3^3\). The expression then becomes \((3^3)^{-4/3}\).
05
Apply the Power of a Power Rule in (b)
Using the rule \((a^m)^n = a^{m \cdot n}\), simplify \((3^3)^{-4/3}\) as follows: \((3^3)^{-4/3} = 3^{3 \times (-4/3)} = 3^{-4}\).
06
Evaluate (b) to a Simplified Form
Now, calculate \(3^{-4}\): This gives \(\frac{1}{3^4} = \frac{1}{81}\). So, \((27)^{-4/3} = \frac{1}{81}\).
07
Expression (c) Simplify the Base
For \(\left(\frac{1}{8}\right)^{-2/3}\), notice that \(8 = 2^3\). Thus, \(\frac{1}{8} = 2^{-3}\), and the expression becomes \((2^{-3})^{-2/3}\).
08
Apply the Power of a Power Rule in (c)
Using the rule \((a^m)^n = a^{m \cdot n}\), simplify \((2^{-3})^{-2/3}\) as follows: \((2^{-3})^{-2/3} = 2^{-3 \times (-2/3)} = 2^2\).
09
Evaluate (c) to a Simplified Form
Now, compute \(2^2\): This is equal to \(4\). Therefore, \(\left(\frac{1}{8}\right)^{-2/3}\) is \(4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power of a Power Rule
When dealing with exponents, the power of a power rule is a powerful tool that can simplify our calculations significantly. This rule states that when you have an exponent raised to another exponent, like \((a^m)^n\), you can multiply these exponents together to obtain the expression \(a^{m \cdot n}\). For example, in the original exercise steps, \((2^{-5})^{2/5}\) was simplified to \(2^{-5 \times 2/5}\) which equals \(2^{-2}\). This rule helps streamline calculations and ensures we avoid long exponent multiplication chains.
The key points to remember with the power of a power rule include:
The key points to remember with the power of a power rule include:
- Only applicable when both base numbers inside and outside the parenthesis are the same.
- Multiply the exponents directly.
- Results in a single exponent which represents a more simplified expression.
Fractional Exponents
Fractional exponents may seem complex at first glance, but they follow a simple principle that relates them to roots. When you have a fractional exponent such as \(a^{m/n}\), it equates to the \(n\)-th root of \(a\) raised to the power \(m\), that is, \((\sqrt[n]{a})^m\). This implies two steps: first, find the root (denominator of the fraction), then raise it to the power (numerator of the fraction).
Using the previous steps, \((27)^{-4/3}\) was simplified using these principles. Recognizing \(27\) as \(3^3\), it was simplified as \((3^3)^{-4/3}\). Using the power of a power rule, it became \(3^{3 \times (-4/3)} = 3^{-4}\). Finally, \(3^{-4}\) relates back to fractional exponents by treating the negative exponent as indicating a reciprocal and computing as \(\frac{1}{3^4}\).
Using the previous steps, \((27)^{-4/3}\) was simplified using these principles. Recognizing \(27\) as \(3^3\), it was simplified as \((3^3)^{-4/3}\). Using the power of a power rule, it became \(3^{3 \times (-4/3)} = 3^{-4}\). Finally, \(3^{-4}\) relates back to fractional exponents by treating the negative exponent as indicating a reciprocal and computing as \(\frac{1}{3^4}\).
- Fractional exponents involve roots and powers, understood as two parts.
- Negative fractional exponents denote reciprocals.
- Simplification turns complex expressions into more manageable forms.
Simplifying Expressions
Simplifying expressions, especially ones with complex exponents, involves combining fundamental rules of exponents to a coherent strategy that ensures all expressions are as simple as possible. Each expression should be broken down using exponent rules systematically. In our steps from the original solution:
- Step 1: Simplify the base. Recognize factors that relate bases to smaller powers or simpler numbers, like \(32 = 2^5\).
- Step 2: Apply exponent rules like the power of a power within these smaller, simpler contexts.
- Step 3: Calculate natural values or simplified fractions to determine precise numerical outputs like \(\frac{1}{81}\) from \(3^{-4}\).