Page 151 - Basic College Mathematics with Early Integers

128 C HAPTE R 2 I INTEGERS AND INTRODUCTION TO VARIABLES

PRACTICE 16 Example 16 Evaluate 2x + y for x = 3 and y =-5.
Evaluate x + 3y for x =-4
and y = 1. Solution: Replace x with 3 and y with -5 in 2x + y.
#
2x + y = 2 3 + 1-52
= 6 + 1-52
= 1
Work Practice 16

PRACTICE 17 Example 17 Evaluate x + y for x =-2 and y =-10.
Evaluate x + y for x =-11
and y =-6. Solution: x + y = 1-22 + 1-102 Replace x with -2 and y with -10.
=-12
PRACTICE 18 Work Practice 17
If the temperature was -8°
Fahrenheit at 6 a.m., and it rose Objective Solving Problems by Adding Integers
4 degrees by 7 a.m. and then
rose another 7 degrees in the Next, we practice solving problems that require adding integers.
hour from 7 a.m. to 8 a.m., what
was the temperature at 8 a.m.? Example 18 Calculating Temperature

On January 6, the temperature in Caribou, Maine, at 8 a.m. was -12° Fahrenheit.
By 9 a.m., the temperature had risen 4 degrees, and by 10 a.m. it had risen
6 degrees from the 9 a.m. temperature.What was the temperature at 10 a.m.?
Solution:
temperature 8 a.m. rise rise
In words: = + +
at 10 a.m. temperature of 4° of 6°
T T T T
temperature
Translate: = -12 + (+4) + (+6)
at 10 a.m.
=-8 + 1+62
= -2
The temperature was -2°F at 10 a.m.
Answers
16. -1 17. -17 18. 3°F Work Practice 18

Calculator Explorations Entering Negative Numbers

To enter a negative number on a calculator, find the key Use a calculator to perform each indicated operation.
marked +/- . (Some calculators have a key marked
1. -256 + 97
CHS and some calculators have a special key (-) for
entering a negative sign.) To enter the number -2, for 2. 811 + 1-10582
example, press the keys 2 +/- . The display will read 3. 61152 + 1-462
-2 .
4. -129 + 101482
To find -32 + 1-1312, press the keys
5. -108,650 + 1-786,2052
32 +/- + 131 +/- = or
6. -196,662 + 1-129,8562
(-) 32 + (-) 131 ENTER Copyright 2012 Pearson Education, Inc.

The display will read -163 . Thus
-32 + 1-1312 =-163.