Absolute Value Inequalities- MathBitsNotebook(A2) (2024)

Absolute Value Inequalities- MathBitsNotebook(A2) (1)

Absolute Value Inequalities
MathBitsNotebook.com

Topical Outline | Algebra 2 Outline | MathBits' Teacher Resources
Terms of Use Contact Person: Donna Roberts Absolute Value Inequalities- MathBitsNotebook(A2) (2)

Solving an absolute value inequality is similar to solving an absolute value equation,
with a few more considerations. When dealing with inequalities, you will be dealing with more possible values as solutions. Check out the following comparisons:

Absolute Value Inequalities- MathBitsNotebook(A2) (3)

LESS THAN: GREATER THAN:

| x | < 2


Absolute Value Inequalities- MathBitsNotebook(A2) (4)
x > -2
and x < 2
also written: -2 < x < 2
| x - 0 | < 2 represents the distance between x and 0 that is less than 2. The solution will be all of the values on the number line between -2 and +2.

| x | > 2


Absolute Value Inequalities- MathBitsNotebook(A2) (5)
x < -2 or x > 2

| x - 0 | > 2 represents the distance between x and 0 that is greater than 2. The solution will be all of the values on the number line to the right of +2 and those to the left of -2.

LESS THAN OR EQUAL TO: GREATER THAN OR EQUAL TO:

| x | < 2
Absolute Value Inequalities- MathBitsNotebook(A2) (6)
x > -2
and x < 2
also written: -2 < x < 2

| x | > 2
Absolute Value Inequalities- MathBitsNotebook(A2) (7)
x < -2 or x > 2

Now, let's formalize these observations into a more mathematical statement:

Absolute Value Inequalities:

If the symbol is < (or <):(and)

If a > 0, then the solutions to | x | < a
are x < a and x > -a.
Also written: -a < x < a

If a < 0, there is no solution to | x | < a.

Think about it: absolute value is always positive (or zero), so, of course, it cannot be less than a negative number.


If the symbol is > (or >):(or)

If a > 0, then the solutions to | x | > a
are x > a or x < -a.

If a < 0, all real numbers will satisfy | x | > a.

Think about it: absolute value is always positive (or zero), so, of course, it is greater than any negative number..


Absolute Value Inequalities- MathBitsNotebook(A2) (8)

For help with solving absolute value inequalities
on your calculator,
click here.

Keep in mind that your graphing calculator can be used to solve absolute value inequalities and/or double check your answers.

Absolute Value Inequalities- MathBitsNotebook(A2) (9)

Absolute Value Inequalities- MathBitsNotebook(A2) (10) Solve for x: | x - 3 | < 4 [Working with "less than or equal to"]

Case 1:
x - 3

<

4
x < 7

and

Case 2:
x - 3

>

-4
x

>

-1

Note that there are two parts to the solution and that the connecting word is "and".

Solution: x > -1 and x < 7
also written as: -1

<

x

<

7

Absolute Value Inequalities- MathBitsNotebook(A2) (11)

Absolute Value Inequalities- MathBitsNotebook(A2) (12) Solve for x: | x - 20 | > 5 [Working with "greater than"]

Case 1:
x - 20 > 5
x > 25

or

Case 2:
x - 20 < -5
x < 15

Note that there are two parts to the solution and that the connecting word is "or".

Solution: x < 15 or x > 25


Absolute Value Inequalities- MathBitsNotebook(A2) (13)

Absolute Value Inequalities- MathBitsNotebook(A2) (14) Solve for x: | 3 + x | - 4 < 0 [Isolate absolute value.]

Case 1:
| 3 + x | < 4
3 + x < 4
x <
1

or

Case 2:
| 3 + x | < 4
3 + x > -4
x > -7

Note that the absolute value is isolated before the solution begins.

Solution: x < 1 and x > -7
also written as: -7 < x < 1


Absolute Value Inequalities- MathBitsNotebook(A2) (15)

Absolute Value Inequalities- MathBitsNotebook(A2) (16) Solve for x: 5 < | x + 1 | < 7 [compound inequality]

Separate a compound inequality into two separate problems.

5 < | x + 1 |

| x + 1 | < 7

Case 1:
5 < x + 1
4 < x

or

Case 2:
-5 > x + 1
-6 > x

Case 1:
x + 1 < 7
x <
6

and

Case 2:
x + 1 < -7
x > -8

Solution: x > 4 or x < -6

Solution: -8 < x < 6

Now, find where the solutions overlap!
Absolute Value Inequalities- MathBitsNotebook(A2) (17)

Solution: -8 < x < -6 as well as 4 < x < 6


Absolute Value Inequalities- MathBitsNotebook(A2) (18)

Absolute Value Inequalities- MathBitsNotebook(A2) (19) Solve for x: | x + 4 | > -3 [All values work.]

Case 1:
x + 4 > -3
x >
-7

or

Case 2:
x + 4 < 3
x < -1

Absolute Value Inequalities- MathBitsNotebook(A2) (20)

You already know the answer!
Absolute value is always positive (or zero),
so it is always > -3.

All values work!

Solution: x > -7 or x < -1
Absolute Value Inequalities- MathBitsNotebook(A2) (21)


Absolute Value Inequalities- MathBitsNotebook(A2) (22)

Absolute Value Inequalities- MathBitsNotebook(A2) (23) Solve for x: | x + 1 | < -6 [No values work.]

Case 1:
x + 1 < -6
x <
-7

and

Case 2:
x + 1 > 6
x > 5

Absolute Value Inequalities- MathBitsNotebook(A2) (24)

You already know the answer!
Absolute value is always positive (or zero).
It is NEVER < -6.

No values work!

Solution: x < -7 and x > 5 ??
The answer is the empty set Ø.


Absolute Value Inequalities- MathBitsNotebook(A2) (25)

Absolute Value Inequalities- MathBitsNotebook(A2) (26) [word problem]
It is reported that the average yearly salary for computer programmers in the United States is $51,423 per year, but can vary depending upon location. The actual salary could differ from the average by as much as $15,559 per year.
a) Write an absolute value inequality to describe this situation.
b) Solve the inequality to find the range of the starting salaries.

Solution:
Remember that | x - a | < b represents the set of all points that are less than b units
away from a.

a) | x - 51423 | < 15559
| the difference between the average and the salary | < $15,559

b)
Case 1:
| x - 51423 | < 15559
x
- 51423 < 15559
x < 66982

Case 2:
| x - 51423 |

<

15559
x - 51423

>

-15559
x

>

35864

Answer: $35,864 < x < $66,982
The absolute value inequality verifies what common sense tells you the answer to be.

Absolute Value Inequalities- MathBitsNotebook(A2) (27)

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Topical Outline | Algebra 2 Outline | MathBitsNotebook.com | MathBits' Teacher Resources Terms of Use Contact Person: Donna Roberts


Absolute Value Inequalities- MathBitsNotebook(A2) (2024)

FAQs

Absolute Value Inequalities- MathBitsNotebook(A2)? ›

Absolute Value Inequalities- MathBitsNotebook(A2) | x - 0 | < 2 represents the distance between x and 0 that is less than 2. The solution will be all of the values on the number line between -2 and +2. | x - 0 | > 2 represents the distance between x and 0 that is greater than 2.

What is the absolute value of a number in MathBitsNotebook? ›

Absolute Value - MathBitsNotebook(A1) The absolute value of a number is the distance between the number and zero on the real number line. Distances are measured as positive units (or zero units). Consequently, absolute value is never negative.

How to solve absolute value inequalities notes? ›

To solve an absolute value inequality involving “less than,” such as |X|≤p, replace it with the compound inequality −p≤X≤p and then solve as usual. To solve an absolute value inequality involving “greater than,” such as |X|≥p, replace it with the compound inequality X≤−p or X≥p and then solve as usual.

What is an absolute value inequality in algebra 2? ›

Absolute value inequalities are inequalities in algebra that involve algebraic expressions with absolute value symbols and inequality symbols. In simple words, we can say that an absolute value inequality is an inequality with an absolute value symbol in it.

Can an absolute value inequality equal zero? ›

If the absolute value is greater than or equal to zero, the solution is all real numbers. d. If the absolute value is greater than zero, the solution is all real numbers except for the value which makes it equal to zero.

How do I solve for absolute value? ›

Follow these steps to solve an absolute value equality which contains one absolute value:
  1. Isolate the absolute value on one side of the equation.
  2. Is the number on the other side of the equation negative? ...
  3. Write two equations without absolute values. ...
  4. Solve the two equations.

What is the absolute value of -|- 71? ›

The absolute value is the distance between a number and zero. The distance between −71 and 0 is 71 .

What is the first step to solve absolute value inequalities? ›

Step 1: Isolate the absolute value|x + 4| - 6 < 9 |x + 4| < 15
Step 2: Is the number on the other side negative?No, it's a positive number, 15. We'll move on to step 3.
Step 3: Set up a compound inequalityThe inequality sign in our problem is a less than sign, so we will set up a 3-part inequality: -15 < x + 4 < 15
1 more row

How to tell if an absolute value inequality has no solution? ›

An absolute value equation has no solution if the absolute value expression equals a negative number since an absolute value can never be negative. You can write an absolute value inequality as a compound inequality. This holds true for all absolute value inequalities. You can replace > above with ≥ and < with ≤.

Can you solve absolute value inequalities by graphing? ›

Solve two variable absolute value inequalities by graphing them. Graph the corresponding absolute value equation. Use a solid line if the inequality includes 'or equal to' or a broken line if it does not. Shade in the appropriate area above or below the line.

What is a real life example of an absolute value inequality? ›

These inequalities involve the absolute value of an expression containing a variable. Through real-world examples, such as determining the acceptable weight range for chocolate bars or understanding the temperature variations on Mars, one can grasp the practical applications of these inequalities.

What does absolute value mean in algebra 2? ›

The absolute value (or modulus) | x | of a real number x is the non-negative value of x without regard to its sign. For example, the absolute value of 5 is 5, and the absolute value of −5 is also 5. The absolute value of a number may be thought of as its distance from zero along real number line.

How to prove inequalities with absolute values? ›

Absolute Value Inequalities are usually proved by the absolute value being greater than or equal to a certain value. The square of the value is equal to the square of its absolute value.

How to solve inequality? ›

When solving an inequality: • you can add the same quantity to each side • you can subtract the same quantity from each side • you can multiply or divide each side by the same positive quantity If you multiply or divide each side by a negative quantity, the inequality symbol must be reversed. So the solution is x > −1.

What is the third step in solving the absolute value inequalities and equations? ›

Isolate the absolute value expression. Write the equivalent compound inequality. Solve the compound inequality. Write the solution using interval notation.

How to simplify absolute value? ›

So, |x| means the absolute value of x, or modulus x. An absolute value expression is an expression that uses the absolute value symbol. To simplify an absolute value expression, write the expression in its simplest form. To do this, the absolute value symbol will be temporarily treated as a set of parentheses.

What is the absolute value of a number in math? ›

Definitions: The absolute value (or modulus) | x | of a real number x is the non-negative value of x without regard to its sign. For example, the absolute value of 5 is 5, and the absolute value of −5 is also 5. The absolute value of a number may be thought of as its distance from zero along real number line.

What will be the absolute value of a number? ›

The absolute value of a number represents its distance from zero on a number line, always resulting in a positive value. This concept is essential in mathematics, as it helps to simplify calculations and understand the magnitude of numbers, regardless of their positive or negative sign.

What is the absolute value of |- 82? ›

The absolute value is the distance between a number and zero. The distance between −82 and 0 is 82 .

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