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Solution - Absolute value equations

Exact form:

z = \frac{5}{2}

z=\frac{5}{2}

Mixed number form:

z = 2 \frac{1}{2}

z=2\frac{1}{2}

Decimal form:

z = 2.5

z=2.5

See steps

Step-by-step explanation

1. Rewrite the equation without absolute value bars

Use the rules:
$| x | = | y |$ → $x = \pm y$ and $| x | = | y |$ → $\pm x = y$
to write all four options of the equation
$| z - 5 | = | z |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| z - 5 \| = \| z \|$
$x = + y$	$(z - 5) = (z)$
$x = - y$	$(z - 5) = - (z)$
$+ x = y$	$(z - 5) = (z)$
$- x = y$	$- (z - 5) = (z)$

When simplified, equations $x = + y$ and $+ x = y$ are the same and equations $x = - y$ and $- x = y$ are the same, so we end up with only 2 equations:

$\| x \| = \| y \|$	$\| z - 5 \| = \| z \|$
$x = + y$ , $+ x = y$	$(z - 5) = (z)$
$x = - y$ , $- x = y$	$(z - 5) = - (z)$

2. Solve the two equations for z

4 additional steps

$(z - 5) = z$

Subtract from both sides:

$(z - 5) - z = z - z$

Group like terms:

$(z - z) - 5 = z - z$

Simplify the arithmetic:

$- 5 = z - z$

Simplify the arithmetic:

$- 5 = 0$

The statement is false:

$- 5 = 0$

The equation is false so it has no solution.

8 additional steps

$(z - 5) = - z$

Add to both sides:

$(z - 5) + z = - z + z$

Group like terms:

$(z + z) - 5 = - z + z$

Simplify the arithmetic:

$2 z - 5 = - z + z$

Simplify the arithmetic:

$2 z - 5 = 0$

Add to both sides:

$(2 z - 5) + 5 = 0 + 5$

Simplify the arithmetic:

$2 z = 0 + 5$

Simplify the arithmetic:

$2 z = 5$

Divide both sides by :

$\frac{(2 z)}{2} = \frac{5}{2}$

Simplify the fraction:

$z = \frac{5}{2}$

3. Graph

Each line represents the function of one side of the equation:
$y = | z - 5 |$
$y = | z |$
The equation is true where the two lines cross.

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Why learn this

We encounter absolute values almost daily. For example: If you walk 3 miles to school, do you also walk minus 3 miles when you go back home? The answer is no because distances use absolute value. The absolute value of the distance between home and school is 3 miles, there or back.
In short, absolute values help us deal with concepts like distance, ranges of possible values, and deviation from a set value.

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation without absolute value bars

2. Solve the two equations for z

3. Graph

Why learn this

Terms and topics

Related links

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation without absolute value bars

2. Solve the two equations for z

3. Graph

Why learn this

Terms and topics

Related links

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