Section 2.5 Order of Operations and Evaluating Expressions
Vocabulary: To evaluate an expression means to replace the variable with
a given value and then simplify.
The process:
• replace each variable with parentheses.
• Write the given value of the variable inside each set of parentheses.
• Use the order of operations to simplify.
EXAMPLES: Evaluate each expression for the given values of the variables. Use the order of operations to simplify.
a) ­9 + 4y for y = 10 and y = ­3
b) ­5y3 ­ y for y = ­1 and y = 2
Tables and Evaluating Expressions
A table can be useful for showing the results from evaluating an
expression for several different values of the variable.
x ­1 0 1 2 x + 1
4 ­ 2x
Work the Your Turn 2 Problem on page153:
y 1 0 ­2 ­4 3y2 y ­ 2 Evaluating Formulas
Some examples of formulas you may have used:
A = l w for a rectangle
A = πr2 for a circle
d = r t for distance
We will use our method for evaluating expressions along with
given formulas in order to solve problems.
EXAMPLE: The formula C = 5F ­ 160
9
converts a temperature in degrees Fahrenheit to degrees Celsius. (round your answer to one decimal place if needed)
What Celsius temperature corresponds to a temperature of ­15℉?
Work the Your Turn 3 problem on page 154:
What Fahrenheit temperature corresponds to a temperature of ­10℃?
9
F = C + 32
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