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This module is from Elementary Algebra by Denny Burzynski and Wade Ellis, Jr. The basic operations with real numbers are presented in this chapter. The concept of absolute value is discussed both geometrically and symbolically. The geometric presentation offers a visual understanding of the meaning of |x|. The symbolic presentation includes a literal explanation of how to use the definition. Negative exponents are developed, using reciprocals and the rules of exponents the student has already learned. Scientific notation is also included, using unique and real-life examples.Objectives of this module: be familiar with positive and negative numbers and with the concept of opposites.

Overview

  • Positive and Negative Numbers
  • Opposites

Positive and negative numbers

When we studied the number line in Section [link] we noted that

Each point on the number line corresponds to a real number, and each real number is located at a unique point on the number line.

A number line with arrows on each end, labeled from negative six to six in increments of one. There are two closed circles at negative two and four, respectively.

Positive and negative numbers

Each real number has a sign inherently associated with it. A real number is said to be a positive number if it is located to the right of 0 on the number line. It is a negative number if it is located to the left of 0 on the number line.

The notation of signed numbers

A number is denoted as positive if it is directly preceded by a " + " sign or no sign at all.
A number is denoted as negative if it is directly preceded by a " " sign.

The " + " and " - " signs now have two meanings:

+ can denote the operation of addition or a positive number.
can denote the operation of subtraction or a negative number.

Read the "-" Sign as "negative"

To avoid any confusion between "sign" and "operation," it is preferable to read the sign of a number as "positive" or "negative."

Sample set a

8 should be read as "negative eight" rather than "minus eight."

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4 + ( 2 ) should be read as "four plus negative two" rather than "four plus minus two."

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6 + ( 3 ) should be read as "negative six plus negative three" rather than "minus six plusminus three."

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15 ( 6 ) should be read as "negative fifteen minus negative six" rather than "minus fifteenminus minus six."

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5 + 7 should be read as "negative five plus seven" rather than "minus five plus seven."

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0 2 should be read as "zero minus two."

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Practice set a

Write each expression in words.

7 + ( 4 )

seven plus negative four

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9 + 2

negative nine plus two

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16 ( + 8 )

negative sixteen minus positive eight

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1 ( 9 )

negative one minus negative nine

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0 + ( 7 )

zero plus negative seven

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Opposites

Opposites

On the number line, each real number has an image on the opposite side of 0. For this reason we say that each real number has an opposite. Opposites are the same distance from zero but have opposite signs.

The opposite of a real number is denoted by placing a negative sign directly in front of the number. Thus, if a is any real number, then a is its opposite. Notice that the letter a is a variable. Thus, " a " need not be positive, and " a " need not be negative.

If a is a real number, a is opposite a on the number line and a is opposite a on the number line.

Two number lines with arrows on each end. The first number line has three labels, zero at the center, negative a to the left of zero and a to the right of zero. Negative a and a are equidistant from zero. The second line has three labels, zero at the center, a to the left of zero and negative a to the right of zero. The points a and negative a are equidistant from zero.

( a ) is opposite a on the number line. This implies that ( a ) = a .

This property of opposites suggests the double-negative property for real numbers.

The double-negative property

If a is a real number, then
( a ) = a

Sample set b

If a = 3 , then a = 3 and ( a ) = ( 3 ) = 3 .

A number line with arrows on each end, labeled from negative three to three in increments of three. Negative three is labeled as negative a, and three is labeled as a. There is an additional label for three as the opposite of negative a.

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If a = 4 , then a = ( 4 ) = 4 and ( a ) = a = 4 .

A number line with arrows on each end, labeled from negative four to four in increments of three. Negative four is labeled as a, and four is labeled as negative a. There is an additional label for negative four as the opposite of negative a.

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Practice set b

Find the opposite of each real number.

( 1 )

1 , since ( 1 ) = 1

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Suppose that a is a positive number. What type of number is a ?

If a is positive, a is negative.

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Suppose that a is a negative number. What type of number is a ?

If a is negative, a is positive.

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Suppose we do not know the sign of the number m . Can we say that m is positive, negative, or that we do notknow ?

We must say that we do not know.

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Exercises

A number is denoted as positive if it is directly preceded by ____________________ .

a plus sign or no sign at all

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A number is denoted as negative if it is directly preceded by ____________________ .

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For the following problems, how should the real numbers be read ? (Write in words.)

( 4 )

negative negative four

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For the following problems, write the expressions in words.

11 + ( 2 )

eleven plus negative two

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6 ( 8 )

six minus negative eight

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Rewrite the following problems in a simpler form.

( 8 )

( 8 ) = 8

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[ ( 3 ) ]

3

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[ ( 6 ) ]

6

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{ [ ( 26 ) ] }

26

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{ [ ( 11 ) ] }

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{ [ ( 31 ) ] }

31

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{ [ ( 14 ) ] }

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5 ( 2 )

5 ( 2 ) = 5 + 2 = 7

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6 ( 3 ) ( 4 )

13

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2 ( 1 ) ( 8 )

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15 ( 6 ) ( 5 )

26

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24 ( 8 ) ( 13 )

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Exercises for review

( [link] ) There is only one real number for which ( 5 a ) 2 = 5 a 2 . What is the number?

0

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( [link] ) Simplify ( 3 x y ) ( 2 x 2 y 3 ) ( 4 x 2 y 4 ) .

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( [link] ) Simplify x n + 3 x 5 .

x n + 8

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( [link] ) Simplify ( a 3 b 2 c 4 ) 4 .

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( [link] ) Simplify ( 4 a 2 b 3 x y 3 ) 2 .

16 a 4 b 2 9 x 2 y 6

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Questions & Answers

how did you get 1640
Noor Reply
If auger is pair are the roots of equation x2+5x-3=0
Peter Reply
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
MATTHEW Reply
420
Sharon
from theory: distance [miles] = speed [mph] × time [hours] info #1 speed_Dennis × 1.5 = speed_Wayne × 2 => speed_Wayne = 0.75 × speed_Dennis (i) info #2 speed_Dennis = speed_Wayne + 7 [mph] (ii) use (i) in (ii) => [...] speed_Dennis = 28 mph speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5. Substituting the first equation into the second: W * 2 = (W + 7) * 1.5 W * 2 = W * 1.5 + 7 * 1.5 0.5 * W = 7 * 1.5 W = 7 * 3 or 21 W is 21 D = W + 7 D = 21 + 7 D = 28
Salma
Devon is 32 32​​ years older than his son, Milan. The sum of both their ages is 54 54​. Using the variables d d​ and m m​ to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
Aaron Reply
find product (-6m+6) ( 3m²+4m-3)
SIMRAN Reply
-42m²+60m-18
Salma
what is the solution
bill
how did you arrive at this answer?
bill
-24m+3+3mÁ^2
Susan
i really want to learn
Amira
I only got 42 the rest i don't know how to solve it. Please i need help from anyone to help me improve my solving mathematics please
Amira
Hw did u arrive to this answer.
Aphelele
hi
Bajemah
-6m(3mA²+4m-3)+6(3mA²+4m-3) =-18m²A²-24m²+18m+18mA²+24m-18 Rearrange like items -18m²A²-24m²+42m+18A²-18
Salma
complete the table of valuesfor each given equatio then graph. 1.x+2y=3
Jovelyn Reply
x=3-2y
Salma
y=x+3/2
Salma
Hi
Enock
given that (7x-5):(2+4x)=8:7find the value of x
Nandala
3x-12y=18
Kelvin
please why isn't that the 0is in ten thousand place
Grace Reply
please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
Stephen
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
Marry Reply
how far
Abubakar
cool u
Enock
state in which quadrant or on which axis each of the following angles given measure. in standard position would lie 89°
Abegail Reply
hello
BenJay
hi
Method
I am eliacin, I need your help in maths
Rood
how can I help
Sir
hmm can we speak here?
Amoon
however, may I ask you some questions about Algarba?
Amoon
hi
Enock
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
cameron Reply
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
mahnoor Reply
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67. Check: Sales = 3542 Commission 12%=425.04 Pay = 500 + 425.04 = 925.04. 925.04 > 925.00
Munster
difference between rational and irrational numbers
Arundhati Reply
When traveling to Great Britain, Bethany exchanged $602 US dollars into £515 British pounds. How many pounds did she receive for each US dollar?
Jakoiya Reply
how to reduced echelon form
Solomon Reply
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?
Zack Reply
d=r×t the equation would be 8/r+24/r+4=3 worked out
Sheirtina
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Source:  OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
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