High School Math : Absolute Value

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Absolute Value

Expression 1: 

Expression 2: 

Find the set of values for  where Expression 1 is greater than Expression 2.

Possible Answers:

All real numbers

All values where 

All values where 

All values where 

All values where 

Correct answer:

All values where 

Explanation:

In finding the values for  where , break the comparison of these two absolute value expressions into the four possible ways this could potentially be satisfied.

The first possibility is described by the inequality:

If you think of a number line, it is evident that there is no solution to this inequality since there will never be a case where subtracting from  will lead to a greater number than adding to .

The second possibility, wherein  is negative and converted to its opposite to being an absolute value expression but  is positive and requires no conversion, can be represented by the inequality (where the sign is inverted due to multiplication by a negative):

We can simplify this inequality to find that  satisfies the conditions where .

The third possibility can be represented by the following inequality (where the sign is inverted due to multiplication by a negative):

This is again simplified to  and is redundant with the above inequality.

The final possibility is represented by the inequality

This inequality simplifies to . Rewriting this as  makes it evident that this inequality is true of all real numbers. This does not provide any additional conditions on how to satisfy the original inequality.

The only possible condition that satisfies the inequality is that which arises in two of the tested cases, when .

Example Question #1 : Mathematical Relationships And Basic Graphs

What is the absolute value of -3? 

Possible Answers:

1

-3

3

10

9

Correct answer:

3

Explanation:

The absolute value is the distance from a given number to 0. In our example, we are given -3. This number is 3 units away from 0, and thus the absolute value of -3 is 3. 

If a number is negative, its absolute value will be the positive number with the same magnitude. If a number is positive, it will be its own absolute value. 

Example Question #1 : Solving Absolute Value Equations

Possible Answers:

Correct answer:

Explanation:

Notice that the equation  has an  term both inside and outside the absolute value expression.

Since the absolute value expression will always produce a positive number and the right side of the equation is negative, a negative number must be added to the result of the absolute value expression to satisfy the equation. Therefore the term outside of the absolute value expression (in this case must be negative (meaning  must be negative). 

Since  will be a negative number, the expression within the absolute value  will also be negative (before the absolute value is taken). It is thus possible to convert the original equation into an equation that treats the absolute value as a parenthetical expression that will be multiplied by , since any negative value becomes its opposite when taking the absolute value.

 

Simplifying and solving this equation for  gives the answer:

Example Question #4 : Absolute Value

What are the possible values for ?

Possible Answers:

Correct answer:

Explanation:

The absolute value measures the distance from zero to the given point. 

In this case, since ,  or , as both values are twelve units away from zero.

Example Question #5 : Absolute Value

Possible Answers:

Correct answer:

Explanation:

Example Question #6 : Absolute Value

Solve:

Possible Answers:

All real numbers

No solution

Correct answer:

Explanation:

The absolute value can never be negative, so the equation is ONLY valid at zero.

The equation to solve becomes

Example Question #7 : Absolute Value

Solve for :

Possible Answers:

Correct answer:

Explanation:

To solve absolute value equations, we must understand that the absoute value function makes a value positive. So when we are solving these problems, we must consider two scenarios, one where the value is positive and one where the value is negative.

 

and 

This gives us:

 and 

 

However, this question has an  outside of the absolute value expression, in this case . Thus, any negative value of  will make the right side of the equation equal to a negative number, which cannot be true for an absolute value expression. Thus,  is an extraneous solution, as  cannot equal a negative number.

 

Our final solution is then

Example Question #1 : Absolute Value

Solve for .

Possible Answers:

Correct answer:

Explanation:

Divide both sides by 3.

Consider both the negative and positive values for the absolute value term.

Subtract 2 from both sides to solve both scenarios for .

Example Question #8 : Absolute Value

Find the -intercepts for the graph given by the equation:

Possible Answers:

Correct answer:

Explanation:

To find the -intercepts, we must set .

To solve absolute value equations, we must understand that the absoute value function makes a value positive. So when we are solving these problems, we must consider two scenarios, one where the value is positive and one where the value is negative.

Now we must set up our two scenarios:

 and 

 and 

 and 

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