Chapter 7: Problem 13
Find all of its square roots. $$ 400 $$
Short Answer
Expert verified
The square roots of 400 are 20 and -20.
Step by step solution
01
- Understand Square Roots
A square root of a number is a value that, when multiplied by itself, gives the original number. Mathematically, if \( x \) is a square root of \( n \), then \( x^2 = n \).
02
- Identify the Positive Square Root
For the given number 400, we need to find \( x \) such that \( x^2 = 400 \). To find the positive square root: \[ x = \sqrt{400} \]. We know that 20 multiplied by 20 equals 400, hence \( \sqrt{400} = 20 \).
03
- Identify the Negative Square Root
For every positive square root, there is also a negative counterpart. Therefore, if \( 20 \) is a square root of 400, \( -20 \) will also be a square root because \( (-20)^2 = 400 \).
04
- List All Square Roots
The two square roots of 400 are 20 and -20.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
positive and negative square roots
When we find the square root of a number, such as 400, we normally look for two roots: one positive and one negative. This is because both a positive and a negative value, when squared, give the original number. For example, both 20 and -20 are square roots of 400 because:
- 20 × 20 = 400
- -20 × -20 = 400
properties of square roots
Square roots have several interesting properties that are helpful when solving mathematical problems:
- Non-negative Principal Square Root: The principal square root refers to the non-negative square root of a number. For 400, the principal square root is 20.
- Symmetry: Square roots are symmetric with respect to zero. This means that for every positive square root, such as 20, there is a corresponding negative square root, -20.
- Multiplicative Property: The square root of a product is the product of the square roots. For example, \(\sqrt{a \cdot b} = \sqrt{a} \cdot \sqrt{b}\). This property makes it easier to simplify complex square root expressions.
- Square of a Square Root: The square of the square root of a number gives the original number back, i.e., \( (\sqrt{n})^2 = n\).
finding square roots
Finding the square root of a number involves determining which value multiplied by itself equals the original number. For instance, we found the square root of 400 as follows:
- Decomposition Method: Break down 400 into its factors, such as 20 × 20. Here, it’s easy to see that both factors are 20, so one square root is 20. The other square root is -20 because \(( -20 )^2 = 400\).
- Using a Calculator: A simple and quick way is to use a calculator to find the square root. Most calculators have a square root function that will yield the principal (positive) square root, which in this case is 20.
- Estimation Method: This involves estimating by finding two closest square numbers. For 400, since it’s between 324 (18^2) and 441 (21^2), we narrow it down to 20. Confirming, we get 20.