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A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change. An algebraic expression contains one or more variables and may contain operation symbols. So p 7 is an algebraic expression. Algebraic Expressions. - PowerPoint PPT Presentation
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2-1 Variables and Expressions
Course 1
A variable is a letter or symbol that represents a quantity that can change.
A constant is a quantity that does not change.
An algebraic expression contains one or more variables and may contain operation symbols. So p 7 is an algebraic expression.
2-1 Variables and Expressions
Course 1
Algebraic Expressions NOT Algebraic Expressions
150 + y 85 ÷ 5
35 w + z 10 + 3 5
2-1 Variables and Expressions
Course 1
Evaluate to find the missing values.
Substitute for y in 5 y.y 5 y
16
27
35
80 y = 16; 5 16 = 80
135
175
27 135
35 175
y = 27; 5 =
y = 35; 5 =
The missing values are 135 and 175.
2-1 Variables and Expressions
Course 1
Evaluate the expression to find the missing values in the table.
z z 5 + 42
20
45
60
20 z = 20; 20 5 + 16 = 20
z = 45; __ 5 + 16 = __
z = 60; __ 5 + 16 = __
25
28
45 25
60 28
The missing values are 25 and 28.
Substitute for z in z 5 + 42.
2-1 Variables and Expressions
Course 1
You can write multiplication and division expressions without using the symbols and .
Instead of . . . You can write . . .
x 3 x 3
35 ÷ y
x(3) 3x
35y
When you are multiplying a number times a variable, the number is written first. Write “3x” not “x3.” Read 3x as “three x.”
Writing Math
2-1 Variables and Expressions
Course 1
A rectangle is 4 units wide. How many square units does the rectangle cover if it is 3, 4, 5, or 6 units long?
Make a table to help you find the number of square units for each length.
3 x 4 = square units
20
16
l w l x w
3 4 12
4 4
5 4
6 4The rectangle will cover 12, 16, 20, or 24 square units.
4 x 4 = square units
5 x 4 = square units
6 x 4 = square units
12
16
20
2424
2-1 Variables and Expressions
Course 1
1. Evaluate the expression to find the missing values in the table.
Lesson Quiz
2. A rectangle is 6 units wide. How many square units does the rectangle cover if it is 2, 3, 4, or 5 units long?
95
44
20
12
l w l x w2 6
3 6
4 6
5 6
18
24
30
x x2 – 5
10
7
5
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