Chapter 11: Problem 42
Use a calculator to evaluate each expression. $$\left(\frac{4 a^{5 / 6} b^{-1 / 5}}{a^{2 / 3} b^{2}}\right)^{-1 / 2}$$
Short Answer
Expert verified
The simplified expression is \(\frac{b^{11/10}}{2a^{1/12}}\). With \(a=1\) and \(b=1\), it simplifies to \(\frac{1}{2}\).
Step by step solution
01
Simplify the Inner Expression - Simplifying the Bases
Rewrite the expression, separating the terms with the same bases. We have the expression \( \frac{4a^{5/6}b^{-1/5}}{a^{2/3}b^{2}} \). Simplify the expression by dealing with the terms with base \(a\) and \(b\). Divide the exponents for \(a\): \(a^{(5/6 - 2/3)} = a^{(5/6 - 4/6)} = a^{1/6}\). Divide the exponents for \(b\): \(b^{-1/5 - 2} = b^{-1/5 - 10/5} = b^{-11/5}\). Thus, the expression becomes \(4a^{1/6}b^{-11/5}\).
02
Apply the Negative Exponent
The entire expression \((4a^{1/6}b^{-11/5})\) is raised to the power of \(-1/2\). Apply the negative half exponent to each part: \((4)^{-1/2} \), \((a^{1/6})^{-1/2} = a^{-(1/6 \cdot 1/2)} = a^{-1/12}\), \((b^{-11/5})^{-1/2} = b^{11/10}\).
03
Calculate the Coefficient
Calculate \( (4)^{-1/2} \). This is equal to \( \frac{1}{4^{1/2}} \), which is \( \frac{1}{2} \), as \( 4^{1/2} \) is 2.
04
Combine the Simplified Expression
Combine the terms:The expression becomes \( \frac{1}{2} \cdot a^{-1/12} \cdot b^{11/10} \).Rewrite for clarity: This is equal to \( \frac{b^{11/10}}{2a^{1/12}} \).
05
Evaluate the Numerical Value Using a Calculator
Convert the expression into numerical form by assuming specific values for \(a\) and \(b\) to evaluate. For simplicity, assume \( a = 1 \) and \( b = 1 \) so \( \frac{1^{11/10}}{2 \cdot 1^{1/12}} = \frac{1}{2}\).
06
Summary: Result Interpretation
Substituting specific values, we found the expression yields \(\frac{1}{2}\). This represents a simplified numerical estimate for the expression under the given assumptions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Negative Exponents
When you see an exponent with a negative sign in expressions, it can initially seem confusing. However, understanding negative exponents is quite straightforward once you grasp the fundamental rule: a negative exponent signifies the reciprocal of the base raised to the corresponding positive exponent.
For example, consider the expression \( b^{-11/5} \). This can be rewritten as \( \frac{1}{b^{11/5}} \). Essentially, the negative sign "flips" the base to the denominator.
Here are some key things to remember about negative exponents:
For example, consider the expression \( b^{-11/5} \). This can be rewritten as \( \frac{1}{b^{11/5}} \). Essentially, the negative sign "flips" the base to the denominator.
Here are some key things to remember about negative exponents:
- The expression \( x^{-n} \) means \( \frac{1}{x^n} \).
- Negative exponents can be used to express division operations through multiplication by reciprocal.
- To simplify an expression with negative exponents, rewrite them as positive by adjusting their position in a fraction.
Exponent Rules
Exponent rules provide a foundation for simplifying expressions and are crucial when dealing with terms that have exponents. The main rules to remember include:
- Product of Powers Rule: When multiplying two expressions that have the same base, you add their exponents: \( x^a \cdot x^b = x^{a+b} \).
- Quotient of Powers Rule: When dividing two expressions with the same base, subtract the exponent in the denominator from the exponent in the numerator: \( \frac{x^a}{x^b} = x^{a-b} \).
- Power of a Power Rule: When raising an expression with an exponent to another power, multiply the exponents: \( (x^a)^b = x^{a \cdot b} \).
- Power of a Product Rule: Apply the exponent to each part of a product: \( (xy)^a = x^a \cdot y^a \).
Calculator Usage
A calculator becomes an invaluable tool in simplifying expressions, especially when dealing with fractional or negative exponents. Here’s how you can make the most of it:
- Entering Exponents: Make sure you use the exponent feature of your calculator, often noted by a \(^\wedge\) or \(\text{EXP}\) button, to input exponents. Double-check your entries, especially with negative or fractional exponents.
- Dealing with Fractions: Convert fractions smoothly by using the division sign when entering a fractional exponent. Some calculators allow direct fractional input, enhancing accuracy.
- Switching Between Forms: For expressions involving negative exponents, you may need to convert them to positive by using the reciprocal function, if manually adjusting is cumbersome.
- Precision: Be aware of the calculator's precision settings. Ensure it displays results to a few significant figures to avoid rounding errors in complex calculations.