1. Lesson 9-3 Warm-Up

2. “Finding and Estimating Square Roots” (9-3) (9-2)
What is the “square root” of a number? What are the parts of “square root”?
square root: The square root, a, of a number, b, is the number that equals b when squared. a is the square root of b in a2 = b The diagram below shows the relationship between squares (a number multiplied by itself) and square roots (the opposite of squaring or the number that needs to be multiplied by itself to equal a given number) Notice that every positive number has two square roots (since a negative times a negative equals a positive) A radical symbol indicate a square root. The number inside the radical sign is called the radicand. You can indicate that a number can be positive or negative with a , which means “plus or minus”. The square root of a negative number is undefined (impossible) meaning you can’t have a negative number inside a radical sign. However, the negative can be outside the radical. This is called a negative square root.(Example: - 16 means “the negative square root of 16.”)

3. “Finding and Estimating Square Roots” (9-3) (9-2)
Examples:

4. Simplify each expression.
Finding and Estimating Square Roots
LESSON 9-3
Additional Examples
Simplify each expression. a
positive square root
= 5
b. ± 9 25 3 5
The square roots are and – .
= ±
c. – 64
negative square root
= –8
d. –49
For real numbers, the square root of a negative
number is undefined.
is undefined 1 16 1 4
The square root is . = e.

5. “Finding and Estimating Square Roots” (9-3) (9-2)
How can you tell if the square root of a number is a rational or irrational number.
The square root of a number is rational if its decimal form terminates (ends) or repeats. Examples: The square root of a number is irrational if its decimal form continues without repeating.

6. Tell whether each expression is rational or irrational.
Finding and Estimating Square Roots
LESSON 9-3
Additional Examples
Tell whether each expression is rational or irrational.
a. ± = ± 12
rational
b = – …
– 1 5
irrational
c. – = –2.5
rational 1 9
d = 0.3
rational
e =
irrational

7. “Finding and Estimating Square Roots” (9-3) (9-2)
What is a perfect square? How can you estimate the square root of a number?.
perfect square: the square of an integer (in other words, an integer times itself) Examples: You can estimate the square root of a number by figuring out what perfect squares its between. Examples: Between what two consecutive integers is is between 3 and 4.

8. Between what two consecutive integers is 28.34 ?
Finding and Estimating Square Roots
LESSON 9-3
Additional Examples
Between what two consecutive integers is ?
28.34 is between the two consecutive perfect squares 25 and 36.
25 < <
The square roots of 25 and 36 are 5 and 6, respectively.
28.34
5 < < 6
28.34 is between 5 and 6.

9. Simplify using PEMDAS (1. Parenthesis)
Finding and Estimating Square Roots
LESSON 9-3
Additional Examples
Suppose a rectangular field has a length three times its width x. The formula d = x2 + (3x)2 gives the distance of the diagonal of a rectangle. Find the length of the diagonal if x = 8 ft.
d = x2 + (3x)2
d = (8)2 + (3 • 8)2
Substitute 8 for x.
d = (8)2 + (24)2
Simplify using PEMDAS (1. Parenthesis)
Simplify using PEMDAS (2. Exponents)
d =
d =
Use a calculator. Round to the nearest tenth. d
The diagonal is about 25.3 ft long.

10. 1. Simplify each expression. a. 196 b. ±
Finding and Estimating Square Roots
LESSON 9-3
Lesson Quiz
1. Simplify each expression.
a         b.  ±
2. Tell whether each expression is rational, irrational, or undefined.
a. ±       b.  –25       c. –
3. Between what two consecutive integers is – 54?
4. The formula s = d estimates the speed s in miles per hour that a car was traveling, when it applied its brakes and left a skid mark d feet long on a wet road. Estimate the speed of a car that left a 120-foot- long skid mark. 4 25 2 5 14 3 5
irrational
undefined
rational
–8 and –7
about mph