1. Square Roots and Real Numbers
1-5
Square Roots and Real Numbers
Holt Algebra 1
Warm Up
Lesson Presentation
Lesson Quiz

2. Warm Up Simplify each expression. 1. 62 2. 112 121 36 25 36
3. (–9)(–9) 81 4.
Write each fraction as a decimal. 2 5 5 9 5.
0.4 6.
0.5 5 3 8 –1 5 6 7.
5.375 8.
–1.83

3. Objectives Evaluate expressions containing square roots.
Classify numbers within the real number system.

4. A number that is multiplied by itself to form a
product is called a square root of that product.
The operations of squaring and finding a square
root are inverse operations.
The radical symbol , is used to represent square roots. Positive real numbers have two
square roots.
= 4
Positive square
root of 16
4  4 = 42 = 16
(–4)(–4) = (–4)2 = 16 –
= –4
Negative square
root of 16

5. The nonnegative square root is represented by
The nonnegative square root is represented by The negative square root is represented by – .
A perfect square is a number whose positive square root is a whole number. Some examples of perfect squares are shown in the table. 1 4 9 16 25 36 49 64 81
100 02 12 22 32 42 52 62 72 82 92
102

6. The expression does not represent
a real number because there is no real number that can be multiplied by itself to form a product of –36.
Reading Math

7. Example 1: Finding Square Roots of
Perfect Squares
Find each square root. A.
Think: What number squared equals 16?
42 = 16
Positive square root positive 4.
= 4 B.
Think: What is the opposite of the
square root of 9?
32 = 9
= –3
Negative square root negative 3.

8. Example 1C: Finding Square Roots of
Perfect Squares
Find the square root.
Think: What number squared equals ? 25 81
Positive square root positive . 5 9

9. The square roots of many numbers like , are not whole numbers
The square roots of many numbers like , are not whole numbers. A calculator can approximate the value of as Without a calculator, you can use square roots of perfect squares to help estimate the square roots of other numbers.

10. Check It Out! Example 2
What if…? Nancy decides to buy more wildflower seeds and now has enough to cover 38 ft2. What is the side length of a square garden with an area of 38 ft2?
Use a guess and check method to estimate
Guess = too low
is greater than 6.1.
Guess = too high
is less than 6.2.
A square garden with a side length of 6.2 ft would have an area of ft ft is close to 38, so 6.2 is a reasonable answer.

11. All numbers that can be represented on a number line are called real numbers and can be classified according to their characteristics.

12. Natural numbers are the counting numbers: 1, 2, 3, …
Whole numbers are the natural numbers and zero:
0, 1, 2, 3, …
Integers are whole numbers and their opposites: –3, –2, –1, 0, 1, 2, 3, …
Rational numbers can be expressed in the form ,
where a and b are both integers and b ≠ 0: , , . a b 1 2 7 9 10

13. Terminating decimals are rational numbers in
decimal form that have a finite number of digits:
1.5, 2.75, 4.0
Repeating decimals are rational numbers in
decimal form that have a block of one or more
digits that repeat continuously: 1.3, 0.6, 2.14
Irrational numbers cannot be expressed in the form . They include square roots of whole numbers that are not perfect squares and nonterminating decimals that do not repeat: ,
,  a b

14. Example 3: Classifying Real Numbers
Write all classifications that apply to each
Real number.
A. –32
32 can be written as a fraction and a decimal. 32 1
–32 = – = –32.0
rational number, integer, terminating decimal
B. 5
5 can be written as a fraction and a decimal. 5 1
5 = = 5.0
rational number, integer, whole number, natural
number, terminating decimal

15. Write all classifications that apply to each real number.
Check It Out! Example 3
Write all classifications that apply to each real number.
7 can be written as a repeating decimal. 49
3a. 7 4 9
67  9 = 7.444… = 7.4
rational number, repeating decimal
3b. –12
32 can be written as a fraction and a decimal.
–12 = – = –12.0
12 1
rational number, terminating decimal, integer
3c.
The digits continue with no pattern.
= …
irrational number

16. Lesson Quiz
Find each square root. 3 7 1 2 -8 1. 12 2. 3. 4. –
5. The area of a square piece of cloth is 68 in2.
How long is each side of the piece of cloth?
Round your answer to the nearest tenth of an
inch.
8.2 in.
Write all classifications that apply to each real number.
rational, integer, whole number, natural number, terminating decimal
6. 1
7. –3.89
rational, repeating decimal 8.
irrational

17. Sec 1-5 Vocab into Definitions section of notebook P. 35-36, #’s 11-40
Assignment
Sec 1-5 Vocab into Definitions section of notebook P , #’s 11-40