Variables in Algebra

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A variable represents an unknown value.
1) 3 ___ 10
These are all variables
2) 6 9
3) 8 x 12
4) 5 8
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Variable Expressions
Variable expressions consist of
constants, variables, and operations.
Example
Meaning
Operation
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Evaluate the expression if a 3, b 4, and c
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1) ab - c
3)
(3)(4) - 5
2(3) 4 2
6 4 2
12 - 5
6 2 8
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2) 2a(b - c)
4)
2(3)(4 - 5)
2(4 5)
2(3)(-1)
3
18
2(9)
-6

6
3
3
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Formulas
Formula - an equation which defines the
relationship of one variable to other variables
or numbers.
Travelling to Las Vegas at an average speed of 60
miles/hour takes 5 hours. How far is Las Vegas?
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Perimeter
Perimeter - Distance around a geometric figure.
Find the perimeter of the triangle below.
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Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
w
l
9
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
10
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
h
b
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Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
h
b
12
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
13
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
h
b
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Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
h
b
15
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
h
b
16
Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
h
b
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Area Formulas
Find the area
Rectangle
w
4
l
5
Parallelogram
8
h
7
b
10
Triangle
7
h
5
b
8
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