Download 2-1

2-1 Variables and Expressions
th
6
Grade Math HW:
Page 50
#5-17 all
Course 1
2-1 Variables and Expressions
Who did not
take the
Chapter 1 Test?
Course 1
2-1 Variables and Expressions
Warm Up
Problem of the Day
Lesson Presentation
Course
Course 11
2-1 Variables and Expressions
Warm Up
Simplify.
1.
2.
3.
4.
Course 1
4+731
87  15  5
6(9 + 2) + 7
35  7  5
24
84
73
25
2-1 Variables and Expressions
Problem of the Day
How can the digits 1 through 5 be arranged
in the boxes to make the greatest product?
4

Course 1
3
5
1
2
2-1 Variables and Expressions
Today’s Learning Goal
Learn to identify
and evaluate
expressions.
Course 1
2-1 Variables and Expressions
Vocabulary
variable
constant
algebraic expression
Course 1
2-1 Variables and Expressions
A variable is a letter or symbol that
represents a quantity that can change.
A constant is a quantity that does
not change.
Course 1
2-1 Variables and Expressions
An algebraic expression contains one or
more variables and may contain operation
symbols. p  7 is an algebraic expression.
Algebraic Expressions
150 + y
35  w + z
NOT Algebraic Expressions
85 ÷ 5
10 + 3  5
To evaluate an algebraic expression, substitute
a number for the variable and then find the
value.
Course 1
2-1 Variables and Expressions
Additional Example 1A: Evaluating Algebraic
Expressions
Evaluate the expression to find the missing
values in the table.
Substitute for y in 5  y.
y
5y
16
80
y = 16; 5  16 = 80
27
135
y = 27; 5  27 = 135
35
175
y = 35; 5  35 = 175
The missing values are 135 and 175.
Course 1
2-1 Variables and Expressions
Additional Example 1B: Evaluating Algebraic
Expressions
Evaluate the expression to find the missing
values in the table.
Substitute for z in z  5 + 4.
z
z5+4
20
8
z = 20; 20  5 + 4 = 8
45
13
z = 45; 45
__  5 + 4 = 13
__
60
16
z = 60; 60
__  5 + 4 = 16
__
The missing values are 13 and 16.
Course 1
2-1 Variables and Expressions
Try This: Example 1A
Evaluate the expression to find the missing
values in the table.
Substitute for x in x  9.
x
x9
18
2
x = 18; 18  9 = 2
36
4
x = 36; 36  9 = 4
54
6
x = 54; 54  9 = 6
The missing values are 4 and 6.
Course 1
2-1 Variables and Expressions
Try This: Example 1B
Evaluate the expression to find the missing
values in the table.
Substitute for z in 8  z + 2.
z
8z+2
7
58
z = 7; 8  7 + 2 = 58
9
74
z = 9; 8  __+
9 2 = __
74
11
90
z = 11; 8  __
11 + 2 = __
90
The missing values are 74 and 90.
Course 1
2-1 Variables and Expressions
Multiplication and division can be written
without using the symbols  and .
Instead of . . .
x3
35 ÷ y
You can write . . .
x3
x(3)
3x
35
y
Writing Math
When you are multiplying a number times
a variable, the number is written first.
Write “3x” not “x3.” Read 3x as “three x.”
Course 1
2-1 Variables and Expressions
Additional Example 2A: Finding an Expression
Find an expression for the table.
n
n  13
39
3
39  13 = 3
52
4
52  13 = 4
65
5
65  13 = 5
An expression is n  13, or n .
13
Course 1
2-1 Variables and Expressions
Additional Example 2B: Finding an Expression
Find an expression for the table.
p
7•p
4
28
7 • 4 = 28
6
42
7 • 6 = 42
8
56
7 • 8 = 56
An expression is 7 • p, or 7p.
Course 1
2-1 Variables and Expressions
Try This: Example 2A
Find an expression for the table.
u
u3
21
7
21  3 = 7
42
14
42  3 = 14
63
21
63  3 = 21
An expression is u  3, or
Course 1
u.
3
2-1 Variables and Expressions
Try This: Example 2B
Find an expression for the table.
n
4•n
5
20
4 • 5 = 20
8
32
4 • 8 = 32
11
44
4 • 11 = 44
An expression is 4 • n, or 4n.
Course 1
2-1 Variables and Expressions
Lesson Quiz: Part 1
1. Evaluate each expression
to find the missing
values in the tables.
2. Find an expression for the
table.
x
x–5
10
5
7
2
5
0
x
7x
1
7
3
21
35
5
Course 1
2-1 Variables and Expressions
Lesson Quiz: Part 2
3. Evaluate 8x for x = 5. 40
4. Evaluate 4x – 1 for x = 12. 47
Course 1