Chapter 3: Problem 3
Evaluate the expression. a. \(9(9)^{-1 / 2}\) b. \(5(5)^{-1 / 2}\)
Short Answer
Expert verified
The given expressions can be evaluated as follows:
a. \(9(9)^{-1/2} = 3\)
b. \(5(5)^{-1/2} \approx 2.23\)
Step by step solution
01
Understand the rational exponent
The exponent -1/2 can be written as a combination of two exponents: -1 and 1/2. When an exponent is -1, it represents taking the reciprocal (i.e., flipping) of the number. When the exponent is 1/2, it represents taking the square root of the number.
So, to evaluate the expression \(9(9)^{-1/2}\), we will first find the square root and then find the reciprocal of the result.
02
Apply the exponent rules
We start by taking the square root of 9 and then finding the reciprocal of the result.
Square root of 9: \(\sqrt{9}=3\)
Reciprocal of the result: \(\frac{1}{3}\)
Now we multiply 9 by the reciprocal of the result:
\(9(\frac{1}{3}) = 3\)
The expression a. \(9(9)^{-1/2}\) simplifies to 3.
For expression b. \(5(5)^{-1/2}\):
03
Understand the rational exponent
As explained before, the exponent -1/2 can be written as a combination of two exponents: -1 and 1/2. When an exponent is -1, it represents taking the reciprocal (i.e., flipping) of the number. When the exponent is 1/2, it represents taking the square root of the number.
So, to evaluate the expression \(5(5)^{-1/2}\), we will first find the square root and then find the reciprocal of the result.
04
Apply the exponent rules
We start by taking the square root of 5 and then finding the reciprocal of the result.
Square root of 5 (rounded to two decimal places): \(\sqrt{5} \approx 2.24\)
Reciprocal of the result: \(\frac{1}{2.24} \approx 0.446\)
Now we multiply 5 by the reciprocal of the result:
\(5(0.446) \approx 2.23\)
The expression b. \(5(5)^{-1/2}\) simplifies to approximately 2.23.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Reciprocal
The reciprocal of a number is basically its flipped version. To find the reciprocal of a number, you swap the numerator with the denominator. If the number is a whole number, you can think of it as being over 1 before flipping it upside down. For example, the reciprocal of 3 is \( \frac{1}{3} \). This concept is handy when dealing with negative exponents.
- When you see \( a^{-1} \), it is the same as \( \frac{1}{a} \).
- In the exercise, the exponent \(-1/2\) means you'll first find the reciprocal after taking the square root.
Square Root
A square root of a number is essentially asking "what number multiplied by itself gives me this number?". Square roots are often represented by the radical symbol \( \sqrt{} \). For example, the square root of 9 is 3, since \(3 \times 3 = 9\).
- In the expressions \(9^{-1/2}\) and \(5^{-1/2}\), the \( \frac{1}{2} \) exponent signifies that we need to find the square root first.
- This is crucial because it transforms the original number into one that can be easily flipped as a reciprocal.
Exponent Rules
Exponent rules are guidelines that make handling exponents manageable, particularly with rational exponents. Some key rules include:
- Product of Powers: \( a^m \times a^n = a^{m+n} \)
- Power of a Power: \( (a^m)^n = a^{m \times n} \)
- Negative Exponent: \( a^{-m} = \frac{1}{a^m} \)
- Rational Exponent: \( a^{\frac{m}{n}} = \sqrt[n]{a^m} \)