Page 176 - Basic College Mathematics with Early Integers

S E C T I O N 2.6 I ORDER OF OPERATIONS 153

Example 14 Evaluate 7 - x 2 for x =-4. PRACTICE 14
Evaluate 4 - x 2 for x =-9.
Solution: Replace x with -4 and simplify carefully!
2 2
7 - x = 7 - 1-42
T T
2
= 7 - 16 1-42 = 1-421-42 = 16
=-9 Subtract.
Work Practice 14

Objective Finding Averages

Recall from Chapter 1 that the average of a list of numbers is
sum of numbers
average =
number of numbers
Example 15 The graph shows some monthly normal temperatures for Barrow, PRACTICE 15
Alaska. Use this graph to find the average of the temperatures for
Find the average of the
the months January through May.
temperatures for the months
Monthly Normal Temperatures for Barrow, Alaska October through April.
30
Degrees Fahrenheit 10 0 15 1 11 1
20
20
10

20
30 14 16 14
Oct Nov Dec Jan Feb Mar Apr May

Solution: By reading the graph, we have
-14 + 1-162 + 1-142 + 1-12 + 20 There are 5 months from
average = January through May.
5
-25
=
5
=-5
The average of the temperatures is -5°F.
Answers
Work Practice 15 14. -77 15. -6°F

Calculator Explorations Simplifying an Expression Containing a Fraction Bar

Recall that even though most calculators follow the order
The display will read 1 .
of operations, parentheses must sometimes be inserted.
-8 + 6 -8 + 6
For example, to simplify on a calculator, enter Thus, = 1.
-2 -2
parentheses about the expression above the fraction bar
so that it is simplified separately. Use a calculator to simplify.
-8 + 6
To simplify , press the keys -120 - 360 4750
-2 1. 2.
-10 -2 + 1-172
( 8 +/- + 6 ) , 2 +/- = or -316 + 1-4582 -234 + 86
3. 4.
( (-) 8 + 6 ) , (-) 2 ENTER 28 + 1-252 -18 + 16