8th Variables and Expressions
To evaluate an expresion means to find its
value
To avoid confusion, mathematicians have agreed to 
a set of          called the order of operations.
When you                       a number for the variable, an algebraic expression becomes a numericalexpression.
A variable is a               , usually a letter, used to
represent a                .
An algebraic expression contains a                   , 
a number, and at least one                   symbol.

substitute
?
number
?
symbol
?
operation
?
variable
?
numeric
?
Evaluate each expression if q = 5, r = 6 and s = 3.
  4(r - s)2
=4
= 4 (    )2

= 4 x 

(
36
?
6
?
9
?
3
?
-
3
)2
Perform operations in the  first.
Evaluate the power.

Simplify
Replace  with 6
and  with 3.
parentheses
?
s
?
r
?
Expressions such a 72 and 23 are called powers
and represent repeated 
Remember q = 5, r = 6 and s = 3.
(
  q2 - 4r - 1
5
?
=
=
=
)
2
25
25
?
1
?
- 4
-
 - 4(6) -1
-  1
(
24
?
6
?
)
- 1
- 1
replace the q with 5
replace the r with 6
Since you have no 
parentheses you must
evaluate the exponents first
Work from left to right when 
operations are the same.
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