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Solution - Absolute value equations

Exact form:

x = - 2, \frac{18}{11}

x=-2 , \frac{18}{11}

Mixed number form:

x = - 2, 1 \frac{7}{11}

x=-2 , 1\frac{7}{11}

Decimal form:

x = - 2, 1.636

x=-2 , 1.636

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
$| 10 x | = | x - 18 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 10 x \| = \| x - 18 \|$
$x = + y$	$(10 x) = (x - 18)$
$x = - y$	$(10 x) = - (x - 18)$
$+ x = y$	$(10 x) = (x - 18)$
$- x = y$	$- (10 x) = (x - 18)$

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:

$\| x \| = \| y \|$	$\| 10 x \| = \| x - 18 \|$
$x = + y$ , $+ x = y$	$(10 x) = (x - 18)$
$x = - y$ , $- x = y$	$(10 x) = - (x - 18)$

2. Solve the two equations for x

7 additional steps

$10 x = (x - 18)$

Subtract from both sides:

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

Simplify the arithmetic:

$9 x = (x - 18) - x$

Group like terms:

$9 x = (x - x) - 18$

Simplify the arithmetic:

$9 x = - 18$

Divide both sides by :

$\frac{(9 x)}{9} = \frac{- 18}{9}$

Simplify the fraction:

$x = \frac{- 18}{9}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 2 \cdot 9)}{(1 \cdot 9)}$

Factor out and cancel the greatest common factor:

$x = - 2$

6 additional steps

$10 x = - (x - 18)$

Expand the parentheses:

$10 x = - x + 18$

Add to both sides:

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

Simplify the arithmetic:

$11 x = (- x + 18) + x$

Group like terms:

$11 x = (- x + x) + 18$

Simplify the arithmetic:

$11 x = 18$

Divide both sides by :

$\frac{(11 x)}{11} = \frac{18}{11}$

Simplify the fraction:

$x = \frac{18}{11}$

3. List the solutions

$x = - 2, \frac{18}{11}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 10 x |$
$y = | x - 18 |$
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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