Ch 1.1 - Variables in Algebra
Objective:
To recognize and evaluate variable
expressions and basic formulas.
Definitions
Variable
A letter that is used to represent a number is
known as a variable.
For example:
In the expression “5x”, x is a variable
representing a number that is multiplied by 5
What is a variable?
A variable represents an unknown value.
1) 3 + ___ = 10
2) 6 +
= 9
3) 8 + x = 12
4) 5 +
= 8
These are all
variables
Variable Expressions
Variable expressions consist of constants,
variables, and operations.
Example
Meaning
Operation
7 times x
multiplication
w divided by 10
division
8p
8 plus p
addition
k 5
k minus 5
subtraction
7x
w
10
Evaluate the expression if a = 3, b = 4,
and c = 5
1) ab - c
(3)(4) - 5
12 - 5
7
2) 2a(b - c)
2(3)(4 - 5)
2(3)(-1)
-6
3) 2a  b  2
2(3) + 4 2
6+4 2
6+2 = 8
2( b  c)
4)
a
2(4 + 5)
3
18
2(9)
=
= 6
3
3