Chapter 1: Problem 103
Should \(\sqrt{9}\) be evaluated as 3 or \(\pm 3\) ?
Short Answer
Expert verified
\(\sqrt{9} = 3\), not \(\pm 3\).
Step by step solution
01
Understanding the Square Root
The square root of a non-negative number, like 9, refers to the non-negative number which, when multiplied by itself, gives the original number (in this case, 9). This is known as the principal square root.
02
Calculating the Principal Square Root of 9
To find the principal square root of 9, determine the positive number which, when squared, gives 9. The number is 3 because \(3^2 = 9\).
03
Exploring ±3: Misconception Clarification
The expression \(\pm 3\) represents two numbers, 3 and -3, both of which are solutions to the equation \(x^2 = 9\). However, \(\sqrt{9}\) is asking specifically for the principal square root, which is just the positive number.
04
Final Decision
Hence, the square root symbol \(\sqrt{}\) only represents the non-negative root, making \(\sqrt{9} = 3\), not \(\pm 3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Principal Square Root
When we talk about the square root of a number, it's crucial to understand the concept of the "principal square root." The principal square root is the non-negative root of a non-negative number. Think of it as the "standard" root we typically refer to when using the square root symbol \( \sqrt{} \). This is crucial because it creates a clear cut way of interpreting square roots without ambiguity.
- It is always positive or zero.
- It simplifies calculations and comparisons by consistently providing a single, except zero, positive value.
Non-negative Number
A non-negative number is a number that is either positive or zero. Understanding non-negative numbers is deeply connected to the principal square root because the square root operation is defined for non-negative numbers only.
- All whole numbers, including zero, are non-negative numbers.
- Fractions and decimals greater than or equal to zero are also non-negative numbers.
Misconception in Mathematics
One common misconception in mathematics occurs when students interpret \( \sqrt{9} \) as \( \pm 3 \). This arises from a misunderstanding of the principal square root concept. While both 3 and -3 satisfy the equation \( x^2 = 9 \), only the non-negative root, 3, is considered as \( \sqrt{9} \). This specific root is the principal square root, not both.
- The principal square root symbol \( \sqrt{ } \) inherently excludes negative numbers.
- Misunderstanding this concept can lead to mistakes in algebra and calculus.