Pre-Algebra Examples

$y = | x | - 5$

Step 1

Find the absolute value vertex. In this case, the vertex for $y = | x | - 5$ is $(0, - 5)$ .

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Step 1.1

To find the $x$ coordinate of the vertex, set the inside of the absolute value $x$ equal to $0$ . In this case, $x = 0$ .

$x = 0$

Step 1.2

Replace the variable $x$ with $0$ in the expression.

$y = | 0 | - 5$

Step 1.3

Simplify $| 0 | - 5$ .

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Step 1.3.1

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

$y = 0 - 5$

Step 1.3.2

Subtract $5$ from $0$ .

$y = - 5$

Step 1.4

The absolute value vertex is $(0, - 5)$ .

$(0, - 5)$

Step 2

The domain of the expression is all real numbers except where the expression is undefined. In this case, there is no real number that makes the expression undefined.

Interval Notation:

$(- \infty, \infty)$

Set-Builder Notation:

${x | x \in ℝ}$

Step 3

For each $x$ value, there is one $y$ value. Select a few $x$ values from the domain. It would be more useful to select the values so that they are around the $x$ value of the absolute value vertex.

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Step 3.1

Substitute the $x$ value $- 2$ into $f (x) = | x | - 5$ . In this case, the point is $(- 2, - 3)$ .

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Step 3.1.1

Replace the variable $x$ with $- 2$ in the expression.

$f (- 2) = | - 2 | - 5$

Step 3.1.2

Simplify the result.

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Step 3.1.2.1

The absolute value is the distance between a number and zero. The distance between $- 2$ and $0$ is $2$ .

$f (- 2) = 2 - 5$

Step 3.1.2.2

Subtract $5$ from $2$ .

$f (- 2) = - 3$

Step 3.1.2.3

The final answer is $- 3$ .

$y = - 3$

Step 3.2

Substitute the $x$ value $- 1$ into $f (x) = | x | - 5$ . In this case, the point is $(- 1, - 4)$ .

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Step 3.2.1

Replace the variable $x$ with $- 1$ in the expression.

$f (- 1) = | - 1 | - 5$

Step 3.2.2

Simplify the result.

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Step 3.2.2.1

The absolute value is the distance between a number and zero. The distance between $- 1$ and $0$ is $1$ .

$f (- 1) = 1 - 5$

Step 3.2.2.2

Subtract $5$ from $1$ .

$f (- 1) = - 4$

Step 3.2.2.3

The final answer is $- 4$ .

$y = - 4$

Step 3.3

Substitute the $x$ value $2$ into $f (x) = | x | - 5$ . In this case, the point is $(2, - 3)$ .

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Step 3.3.1

Replace the variable $x$ with $2$ in the expression.

$f (2) = | 2 | - 5$

Step 3.3.2

Simplify the result.

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Step 3.3.2.1

The absolute value is the distance between a number and zero. The distance between $0$ and $2$ is $2$ .

$f (2) = 2 - 5$

Step 3.3.2.2

Subtract $5$ from $2$ .

$f (2) = - 3$

Step 3.3.2.3

The final answer is $- 3$ .

$y = - 3$

Step 3.4

The absolute value can be graphed using the points around the vertex $(0, - 5), (- 2, - 3), (- 1, - 4), (1, - 4), (2, - 3)$

$\begin{array}{c} x & y \\ - 2 & - 3 \\ - 1 & - 4 \\ 0 & - 5 \\ 1 & - 4 \\ 2 & - 3 \end{array}$

Step 4