2.7 Linear inequalities and absolute value inequalities

 Page 1 / 11
In this section you will:
• Use interval notation.
• Use properties of inequalities.
• Solve inequalities in one variable algebraically.
• Solve absolute value inequalities.

It is not easy to make the honor role at most top universities. Suppose students were required to carry a course load of at least 12 credit hours and maintain a grade point average of 3.5 or above. How could these honor roll requirements be expressed mathematically? In this section, we will explore various ways to express different sets of numbers, inequalities, and absolute value inequalities.

Using interval notation

Indicating the solution to an inequality such as $\text{\hspace{0.17em}}x\ge 4\text{\hspace{0.17em}}$ can be achieved in several ways.

We can use a number line as shown in [link] . The blue ray begins at $\text{\hspace{0.17em}}x=4\text{\hspace{0.17em}}$ and, as indicated by the arrowhead, continues to infinity, which illustrates that the solution set includes all real numbers greater than or equal to 4.

We can use set-builder notation : $\text{\hspace{0.17em}}\left\{x|x\ge 4\right\},$ which translates to “all real numbers x such that x is greater than or equal to 4.” Notice that braces are used to indicate a set.

The third method is interval notation    , in which solution sets are indicated with parentheses or brackets. The solutions to $\text{\hspace{0.17em}}x\ge 4\text{\hspace{0.17em}}$ are represented as $\text{\hspace{0.17em}}\left[4,\infty \right).\text{\hspace{0.17em}}$ This is perhaps the most useful method, as it applies to concepts studied later in this course and to other higher-level math courses.

The main concept to remember is that parentheses represent solutions greater or less than the number, and brackets represent solutions that are greater than or equal to or less than or equal to the number. Use parentheses to represent infinity or negative infinity, since positive and negative infinity are not numbers in the usual sense of the word and, therefore, cannot be “equaled.” A few examples of an interval    , or a set of numbers in which a solution falls, are $\text{\hspace{0.17em}}\left[-2,6\right),$ or all numbers between $\text{\hspace{0.17em}}-2\text{\hspace{0.17em}}$ and $\text{\hspace{0.17em}}6,$ including $\text{\hspace{0.17em}}-2,$ but not including $\text{\hspace{0.17em}}6;$ $\left(-1,0\right),$ all real numbers between, but not including $\text{\hspace{0.17em}}-1\text{\hspace{0.17em}}$ and $\text{\hspace{0.17em}}0;$ and $\text{\hspace{0.17em}}\left(-\infty ,1\right],$ all real numbers less than and including $\text{\hspace{0.17em}}1.\text{\hspace{0.17em}}$ [link] outlines the possibilities.

Set Indicated Set-Builder Notation Interval Notation
All real numbers between a and b , but not including a or b $\left\{x|a $\left(a,b\right)$
All real numbers greater than a , but not including a $\left\{x|x>a\right\}$ $\left(a,\infty \right)$
All real numbers less than b , but not including b $\left\{x|x $\left(-\infty ,b\right)$
All real numbers greater than a , including a $\left\{x|x\ge a\right\}$ $\left[a,\infty \right)$
All real numbers less than b , including b $\left\{x|x\le b\right\}$ $\left(-\infty ,b\right]$
All real numbers between a and b , including a $\left\{x|a\le x $\left[a,b\right)$
All real numbers between a and b , including b $\left\{x|a $\left(a,b\right]$
All real numbers between a and b , including a and b $\left\{x|a\le x\le b\right\}$ $\left[a,b\right]$
All real numbers less than a or greater than b $\left\{x|xb\right\}$ $\left(-\infty ,a\right)\cup \left(b,\infty \right)$
All real numbers $\left(-\infty ,\infty \right)$

Using interval notation to express all real numbers greater than or equal to a

Use interval notation to indicate all real numbers greater than or equal to $\text{\hspace{0.17em}}-2.$

Use a bracket on the left of $\text{\hspace{0.17em}}-2\text{\hspace{0.17em}}$ and parentheses after infinity: $\text{\hspace{0.17em}}\left[-2,\infty \right).$ The bracket indicates that $\text{\hspace{0.17em}}-2\text{\hspace{0.17em}}$ is included in the set with all real numbers greater than $\text{\hspace{0.17em}}-2\text{\hspace{0.17em}}$ to infinity.

Use interval notation to indicate all real numbers between and including $\text{\hspace{0.17em}}-3\text{\hspace{0.17em}}$ and $\text{\hspace{0.17em}}5.$

$\left[-3,5\right]$

x exposant 4 + 4 x exposant 3 + 8 exposant 2 + 4 x + 1 = 0
x exposent4+4x exposent3+8x exposent2+4x+1=0
HERVE
How can I solve for a domain and a codomains in a given function?
ranges
EDWIN
Thank you I mean range sir.
Oliver
proof for set theory
don't you know?
Inkoom
find to nearest one decimal place of centimeter the length of an arc of circle of radius length 12.5cm and subtending of centeral angle 1.6rad
factoring polynomial
find general solution of the Tanx=-1/root3,secx=2/root3
find general solution of the following equation
Nani
the value of 2 sin square 60 Cos 60
0.75
Lynne
0.75
Inkoom
when can I use sin, cos tan in a giving question
depending on the question
Nicholas
I am a carpenter and I have to cut and assemble a conventional roof line for a new home. The dimensions are: width 30'6" length 40'6". I want a 6 and 12 pitch. The roof is a full hip construction. Give me the L,W and height of rafters for the hip, hip jacks also the length of common jacks.
John
I want to learn the calculations
where can I get indices
I need matrices
Nasasira
hi
Raihany
Hi
Solomon
need help
Raihany
maybe provide us videos
Nasasira
Raihany
Hello
Cromwell
a
Amie
What do you mean by a
Cromwell
nothing. I accidentally press it
Amie
you guys know any app with matrices?
Khay
Ok
Cromwell
Solve the x? x=18+(24-3)=72
x-39=72 x=111
Suraj
Solve the formula for the indicated variable P=b+4a+2c, for b
Need help with this question please
b=-4ac-2c+P
Denisse
b=p-4a-2c
Suddhen
b= p - 4a - 2c
Snr
p=2(2a+C)+b
Suraj
b=p-2(2a+c)
Tapiwa
P=4a+b+2C
COLEMAN
b=P-4a-2c
COLEMAN
like Deadra, show me the step by step order of operation to alive for b
John
A laser rangefinder is locked on a comet approaching Earth. The distance g(x), in kilometers, of the comet after x days, for x in the interval 0 to 30 days, is given by g(x)=250,000csc(π30x). Graph g(x) on the interval [0, 35]. Evaluate g(5)  and interpret the information. What is the minimum distance between the comet and Earth? When does this occur? To which constant in the equation does this correspond? Find and discuss the meaning of any vertical asymptotes.
The sequence is {1,-1,1-1.....} has