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Solution - Absolute value equations

Exact form:

x = 3

x=3

See steps

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

$| 2 x - 8 | - | 2 x - 4 | = 0$

Add $| 2 x - 4 |$ to both sides of the equation:

$| 2 x - 8 | - | 2 x - 4 | + | 2 x - 4 | = | 2 x - 4 |$

Simplify the arithmetic

$| 2 x - 8 | = | 2 x - 4 |$

2. 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
$| 2 x - 8 | = | 2 x - 4 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 2 x - 8 \| = \| 2 x - 4 \|$
$x = + y$	$(2 x - 8) = (2 x - 4)$
$x = - y$	$(2 x - 8) = (- (2 x - 4))$
$+ x = y$	$(2 x - 8) = (2 x - 4)$
$- x = y$	$- (2 x - 8) = (2 x - 4)$

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:

$\| x \| = \| y \|$	$\| 2 x - 8 \| = \| 2 x - 4 \|$
$x = + y$ , $+ x = y$	$(2 x - 8) = (2 x - 4)$
$x = - y$ , $- x = y$	$(2 x - 8) = (- (2 x - 4))$

3. Solve the two equations for x

5 additional steps

$(2 x - 8) = (2 x - 4)$

Subtract from both sides:

$(2 x - 8) - 2 x = (2 x - 4) - 2 x$

Group like terms:

$(2 x - 2 x) - 8 = (2 x - 4) - 2 x$

Simplify the arithmetic:

$- 8 = (2 x - 4) - 2 x$

Group like terms:

$- 8 = (2 x - 2 x) - 4$

Simplify the arithmetic:

$- 8 = - 4$

The statement is false:

$- 8 = - 4$

The equation is false so it has no solution.

12 additional steps

$(2 x - 8) = - (2 x - 4)$

Expand the parentheses:

$(2 x - 8) = - 2 x + 4$

Add to both sides:

$(2 x - 8) + 2 x = (- 2 x + 4) + 2 x$

Group like terms:

$(2 x + 2 x) - 8 = (- 2 x + 4) + 2 x$

Simplify the arithmetic:

$4 x - 8 = (- 2 x + 4) + 2 x$

Group like terms:

$4 x - 8 = (- 2 x + 2 x) + 4$

Simplify the arithmetic:

$4 x - 8 = 4$

Add to both sides:

$(4 x - 8) + 8 = 4 + 8$

Simplify the arithmetic:

$4 x = 4 + 8$

Simplify the arithmetic:

$4 x = 12$

Divide both sides by :

$\frac{(4 x)}{4} = \frac{12}{4}$

Simplify the fraction:

$x = \frac{12}{4}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(3 \cdot 4)}{(1 \cdot 4)}$

Factor out and cancel the greatest common factor:

$x = 3$

4. Graph

Each line represents the function of one side of the equation:
$y = | 2 x - 8 |$
$y = | 2 x - 4 |$
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 with one absolute value terms on each side

2. Rewrite the equation without absolute value bars

3. Solve the two equations for x

4. Graph

Why learn this

Terms and topics

Related links

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

2. Rewrite the equation without absolute value bars

3. Solve the two equations for x

4. Graph

Why learn this

Terms and topics

Related links

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