# 3.6 Absolute value functions  (Page 3/3)

 Page 3 / 3

Access these online resources for additional instruction and practice with absolute value.

## Key concepts

• Applied problems, such as ranges of possible values, can also be solved using the absolute value function. See [link] .
• The graph of the absolute value function resembles a letter V. It has a corner point at which the graph changes direction. See [link] .
• In an absolute value equation, an unknown variable is the input of an absolute value function.
• If the absolute value of an expression is set equal to a positive number, expect two solutions for the unknown variable. See [link] .

## Verbal

How do you solve an absolute value equation?

Isolate the absolute value term so that the equation is of the form $\text{\hspace{0.17em}}|A|=B.\text{\hspace{0.17em}}$ Form one equation by setting the expression inside the absolute value symbol, $\text{\hspace{0.17em}}A,\text{\hspace{0.17em}}$ equal to the expression on the other side of the equation, $\text{\hspace{0.17em}}B.\text{\hspace{0.17em}}$ Form a second equation by setting $\text{\hspace{0.17em}}A\text{\hspace{0.17em}}$ equal to the opposite of the expression on the other side of the equation, $\text{\hspace{0.17em}}-B.\text{\hspace{0.17em}}$ Solve each equation for the variable.

How can you tell whether an absolute value function has two x -intercepts without graphing the function?

When solving an absolute value function, the isolated absolute value term is equal to a negative number. What does that tell you about the graph of the absolute value function?

The graph of the absolute value function does not cross the $\text{\hspace{0.17em}}x$ -axis, so the graph is either completely above or completely below the $\text{\hspace{0.17em}}x$ -axis.

How can you use the graph of an absolute value function to determine the x -values for which the function values are negative?

## Algebraic

Describe all numbers $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ that are at a distance of 4 from the number 8. Express this set of numbers using absolute value notation.

Describe all numbers $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ that are at a distance of $\text{\hspace{0.17em}}\frac{1}{2}\text{\hspace{0.17em}}$ from the number −4. Express this set of numbers using absolute value notation.

$\text{\hspace{0.17em}}|x+4|=\frac{1}{2}\text{\hspace{0.17em}}$

Describe the situation in which the distance that point $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ is from 10 is at least 15 units. Express this set of numbers using absolute value notation.

Find all function values $\text{\hspace{0.17em}}f\left(x\right)\text{\hspace{0.17em}}$ such that the distance from $\text{\hspace{0.17em}}f\left(x\right)\text{\hspace{0.17em}}$ to the value 8 is less than 0.03 units. Express this set of numbers using absolute value notation.

$|f\left(x\right)-8|<0.03$

For the following exercises, find the x - and y -intercepts of the graphs of each function.

$f\left(x\right)=4|x-3|+4$

$f\left(x\right)=-3|x-2|-1$

$\left(0,-7\right);\text{\hspace{0.17em}}$ no $\text{\hspace{0.17em}}x$ -intercepts

$f\left(x\right)=-2|x+1|+6$

$f\left(x\right)=-5|x+2|+15$

$\left(0,\text{\hspace{0.17em}}5\right),\left(1,0\right),\left(-5,0\right)$

$f\left(x\right)=2|x-1|-6$

$\left(0,-4\right),\left(4,0\right),\left(-2,0\right)$

$f\left(x\right)=|-2x+1|-13$

$\left(0,-12\right),\left(-6,0\right),\left(7,0\right)$

$f\left(x\right)=-|x-9|+16$

$\left(0,7\right),\left(25,0\right),\left(-7,0\right)$

## Graphical

For the following exercises, graph the absolute value function. Plot at least five points by hand for each graph.

$y=|x-1|$

$y=|x+1|$

$y=|x|+1$

For the following exercises, graph the given functions by hand.

$y=|x|-2$

$y=-|x|$

$y=-|x|-2$

$y=-|x-3|-2$

$f\left(x\right)=-|x-1|-2$

$f\left(x\right)=-|x+3|+4$

$f\left(x\right)=2|x+3|+1$

$f\left(x\right)=3|x-2|+3$

$f\left(x\right)=|2x-4|-3$

$f\left(x\right)=|3x+9|+2$

$f\left(x\right)=-|x-1|-3$

$f\left(x\right)=-|x+4|-3$

$f\left(x\right)=\frac{1}{2}|x+4|-3$

## Technology

Use a graphing utility to graph $f\left(x\right)=10|x-2|$ on the viewing window $\left[0,4\right].$ Identify the corresponding range. Show the graph.

range: $\text{\hspace{0.17em}}\left[0,20\right]$

Use a graphing utility to graph $\text{\hspace{0.17em}}f\left(x\right)=-100|x|+100\text{\hspace{0.17em}}$ on the viewing window $\text{\hspace{0.17em}}\left[-5,5\right].\text{\hspace{0.17em}}$ Identify the corresponding range. Show the graph.

For the following exercises, graph each function using a graphing utility. Specify the viewing window.

$f\left(x\right)=-0.1|0.1\left(0.2-x\right)|+0.3$

$x\text{-}$ intercepts:

$f\left(x\right)=4×{10}^{9}|x-\left(5×{10}^{9}\right)|+2×{10}^{9}$

## Extensions

For the following exercises, solve the inequality.

If possible, find all values of $a$ such that there are no $x\text{-}$ intercepts for $f\left(x\right)=2|x+1|+a.$

If possible, find all values of $\text{\hspace{0.17em}}a\text{\hspace{0.17em}}$ such that there are no $\text{\hspace{0.17em}}y$ -intercepts for $\text{\hspace{0.17em}}f\left(x\right)=2|x+1|+a.$

There is no solution for $\text{\hspace{0.17em}}a\text{\hspace{0.17em}}$ that will keep the function from having a $\text{\hspace{0.17em}}y$ -intercept. The absolute value function always crosses the $\text{\hspace{0.17em}}y$ -intercept when $\text{\hspace{0.17em}}x=0.$

## Real-world applications

Cities A and B are on the same east-west line. Assume that city A is located at the origin. If the distance from city A to city B is at least 100 miles and $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ represents the distance from city B to city A, express this using absolute value notation.

The true proportion $\text{\hspace{0.17em}}p\text{\hspace{0.17em}}$ of people who give a favorable rating to Congress is 8% with a margin of error of 1.5%. Describe this statement using an absolute value equation.

$|p-0.08|\le 0.015$

Students who score within 18 points of the number 82 will pass a particular test. Write this statement using absolute value notation and use the variable $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ for the score.

A machinist must produce a bearing that is within 0.01 inches of the correct diameter of 5.0 inches. Using $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ as the diameter of the bearing, write this statement using absolute value notation.

$|x-5.0|\le 0.01$

The tolerance for a ball bearing is 0.01. If the true diameter of the bearing is to be 2.0 inches and the measured value of the diameter is $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ inches, express the tolerance using absolute value notation.

#### Questions & Answers

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Mark Reply
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Miranda
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Miranda Drice
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Miranda
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Miranda
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Propessor Reply
I think the formula for calculating algebraic is the statement of the equality of two expression stimulate by a set of addition, multiplication, soustraction, division, raising to a power and extraction of Root. U believe by having those in the equation you will be in measure to calculate it
Miranda
state and prove Cayley hamilton therom
sita Reply
hello
Propessor
hi
Miranda
the Cayley hamilton Theorem state if A is a square matrix and if f(x) is its characterics polynomial then f(x)=0 in another ways evey square matrix is a root of its chatacteristics polynomial.
Miranda
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jai
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Propessor
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Pearl Reply
algebra is a branch of the mathematics to calculate expressions follow.
Miranda
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Jeffrey
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Miranda
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Steve
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Steve
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Jeffrey
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Miranda
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Nelson Reply
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Miranda
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Jeffrey
answer and questions in exercise 11.2 sums
Yp Reply
how do u calculate inequality of irrational number?
Alaba
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Chris
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Chris
cos (-z)= cos z .
Swadesh
cos(- z)=cos z
Mustafa
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Jallah Reply
(x+x)3=?
Narad
6x
Obed
what is the identity of 1-cos²5x equal to?
liyemaikhaya Reply
__john __05
Kishu
Hi
Abdel
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Nokwanda
C'est comment
Abdel
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SORIE
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SORIE
it's 12
what is the function of sine with respect of cosine , graphically
Karl Reply
tangent bruh
Steve
cosx.cos2x.cos4x.cos8x
Aashish Reply
sinx sin2x is linearly dependent
cr Reply
what is a reciprocal
Ajibola Reply
The reciprocal of a number is 1 divided by a number. eg the reciprocal of 10 is 1/10 which is 0.1
Shemmy
Reciprocal is a pair of numbers that, when multiplied together, equal to 1. Example; the reciprocal of 3 is ⅓, because 3 multiplied by ⅓ is equal to 1
Jeza
each term in a sequence below is five times the previous term what is the eighth term in the sequence
Funmilola Reply
I don't understand how radicals works pls
Kenny Reply
How look for the general solution of a trig function
collins Reply

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