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Solution - Absolute value equations

Exact form:

x = - 5, - \frac{3}{5}

x=-5 , -\frac{3}{5}

Decimal form:

x = - 5, - 0.6

x=-5 , -0.6

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
$| 2 x - 12 | = | 8 x + 18 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 2 x - 12 \| = \| 8 x + 18 \|$
$x = + y$	$(2 x - 12) = (8 x + 18)$
$x = - y$	$(2 x - 12) = - (8 x + 18)$
$+ x = y$	$(2 x - 12) = (8 x + 18)$
$- x = y$	$- (2 x - 12) = (8 x + 18)$

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:

$\| x \| = \| y \|$	$\| 2 x - 12 \| = \| 8 x + 18 \|$
$x = + y$ , $+ x = y$	$(2 x - 12) = (8 x + 18)$
$x = - y$ , $- x = y$	$(2 x - 12) = - (8 x + 18)$

2. Solve the two equations for x

13 additional steps

$(2 x - 12) = (8 x + 18)$

Subtract from both sides:

$(2 x - 12) - 8 x = (8 x + 18) - 8 x$

Group like terms:

$(2 x - 8 x) - 12 = (8 x + 18) - 8 x$

Simplify the arithmetic:

$- 6 x - 12 = (8 x + 18) - 8 x$

Group like terms:

$- 6 x - 12 = (8 x - 8 x) + 18$

Simplify the arithmetic:

$- 6 x - 12 = 18$

Add to both sides:

$(- 6 x - 12) + 12 = 18 + 12$

Simplify the arithmetic:

$- 6 x = 18 + 12$

Simplify the arithmetic:

$- 6 x = 30$

Divide both sides by :

$\frac{(- 6 x)}{- 6} = \frac{30}{- 6}$

Cancel out the negatives:

$\frac{6 x}{6} = \frac{30}{- 6}$

Simplify the fraction:

$x = \frac{30}{- 6}$

Move the negative sign from the denominator to the numerator:

$x = \frac{- 30}{6}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 5 \cdot 6)}{(1 \cdot 6)}$

Factor out and cancel the greatest common factor:

$x = - 5$

12 additional steps

$(2 x - 12) = - (8 x + 18)$

Expand the parentheses:

$(2 x - 12) = - 8 x - 18$

Add to both sides:

$(2 x - 12) + 8 x = (- 8 x - 18) + 8 x$

Group like terms:

$(2 x + 8 x) - 12 = (- 8 x - 18) + 8 x$

Simplify the arithmetic:

$10 x - 12 = (- 8 x - 18) + 8 x$

Group like terms:

$10 x - 12 = (- 8 x + 8 x) - 18$

Simplify the arithmetic:

$10 x - 12 = - 18$

Add to both sides:

$(10 x - 12) + 12 = - 18 + 12$

Simplify the arithmetic:

$10 x = - 18 + 12$

Simplify the arithmetic:

$10 x = - 6$

Divide both sides by :

$\frac{(10 x)}{10} = \frac{- 6}{10}$

Simplify the fraction:

$x = \frac{- 6}{10}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 3 \cdot 2)}{(5 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = \frac{- 3}{5}$

3. List the solutions

$x = - 5, - \frac{3}{5}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 2 x - 12 |$
$y = | 8 x + 18 |$
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 x

3. List the solutions

4. 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 x

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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