Chapter 8: Problem 122
Simplify each expression. Write answers using only positive exponents. $$ \left(\frac{a^{-2} b^{3} a^{5} b^{-2}}{a^{6} b^{-5}}\right)^{-4} $$
Short Answer
Expert verified
The simplified expression is \( \frac{a^{12}}{b^{24}} \).
Step by step solution
01
Simplify the Expression Inside the Parentheses
First, let's simplify the expression inside the parentheses. The given expression is \( \frac{a^{-2} b^{3} a^{5} b^{-2}}{a^{6} b^{-5}} \). Begin by combining the exponents for like bases in the numerator: \( a^{-2} \cdot a^{5} = a^{-2+5} = a^{3} \) and \( b^{3} \cdot b^{-2} = b^{3-2} = b^{1} = b \). This simplifies the numerator to \( a^{3} b^{1} \) or just \( a^{3} b \). So the expression becomes \( \frac{a^{3} b}{a^{6} b^{-5}} \).
02
Apply the Quotient Rule for Exponents
Now let's use the quotient rule \( \frac{x^m}{x^n} = x^{m-n} \) to simplify the fraction: \[ \frac{a^{3} b^{1}}{a^{6} b^{-5}} = a^{3-6} b^{1-(-5)} = a^{-3} b^{6} \]. Now, the expression inside the parentheses is \( a^{-3} b^{6} \).
03
Apply the Negative Exponent
The entire expression is raised to the power of \(-4\) as follows: \( \left(a^{-3} b^{6}\right)^{-4} \). Using the power of a power rule \((x^m)^n = x^{m \cdot n}\), we simplify know that: \[ a^{-3 \cdot (-4)} b^{6 \cdot (-4)} = a^{12} b^{-24} \].
04
Convert Negative Exponents to Positive
Finally, to express the expression with only positive exponents, write \( b^{-24} \) as \( \frac{1}{b^{24}} \): \[ a^{12} b^{-24} = \frac{a^{12}}{b^{24}} \]. Thus, the simplified expression is \( \frac{a^{12}}{b^{24}} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponent Rules
Exponent rules are a helpful tool when dealing with mathematical expressions involving powers. These rules simplify expressions and make them easier to work with. Here are some key exponent rules you should know:
- Product of Powers Rule: When you multiply two powers with the same base, you add the exponents together. For example, \( a^m \times a^n = a^{m+n} \).
- Power of a Power Rule: When raising an exponent to another power, you multiply the exponents. This means \( (x^m)^n = x^{m \cdot n} \).
- Quotient Rule: This rule is used when dividing two powers with the same base. You subtract the exponent of the denominator from the exponent of the numerator: \( \frac{x^m}{x^n} = x^{m-n} \).
Negative Exponents
Negative exponents can initially seem confusing, but they follow a simple principle. A negative exponent indicates the reciprocal of the base raised to the opposite positive exponent. For example, \( a^{-n} \) is equivalent to \( \frac{1}{a^n} \). This means that rather than multiplying a number by itself negatively, you divide 1 by the number raised to the positive version of the exponent.
Let's see how negative exponents play out in simplification:
Let's see how negative exponents play out in simplification:
- When you encounter an expression such as \( a^{-3} \), this translates to \( \frac{1}{a^3} \).
- If a negative exponent appears in a numerator or a denominator, use the reciprocal to make the exponent positive. For example, \( \frac{b^{-2}}{1} = \frac{1}{b^2} \).
Quotient Rule
The quotient rule is invaluable for simplifying expressions where you divide like bases with exponents. The formula \( \frac{x^m}{x^n} = x^{m-n} \) allows us to subtract the exponent of the denominator from the exponent of the numerator. This rule is straightforward: if the base is the same, you only need to focus on subtracting the exponents.
Here's an example of using the quotient rule:
Here's an example of using the quotient rule:
- Consider \( \frac{a^5}{a^3} \). Using the quotient rule, you have \( a^{5-3} = a^2 \).
- If the exponent of the numerator is smaller, you end up with a negative exponent, such as \( \frac{a^2}{a^5} = a^{2-5} = a^{-3} \). This can further be rewritten as \( \frac{1}{a^3} \) using the rules for negative exponents.