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Solution - Absolute value equations

Exact form:

x = 19, - \frac{17}{3}

x=19 , -\frac{17}{3}

Mixed number form:

x = 19, - 5 \frac{2}{3}

x=19 , -5\frac{2}{3}

Decimal form:

x = 19, - 5.667

x=19 , -5.667

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
$| 2 x - 1 | = | x + 18 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 2 x - 1 \| = \| x + 18 \|$
$x = + y$	$(2 x - 1) = (x + 18)$
$x = - y$	$(2 x - 1) = - (x + 18)$
$+ x = y$	$(2 x - 1) = (x + 18)$
$- x = y$	$- (2 x - 1) = (x + 18)$

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:

$\| x \| = \| y \|$	$\| 2 x - 1 \| = \| x + 18 \|$
$x = + y$ , $+ x = y$	$(2 x - 1) = (x + 18)$
$x = - y$ , $- x = y$	$(2 x - 1) = - (x + 18)$

2. Solve the two equations for x

7 additional steps

$(2 x - 1) = (x + 18)$

Subtract from both sides:

$(2 x - 1) - x = (x + 18) - x$

Group like terms:

$(2 x - x) - 1 = (x + 18) - x$

Simplify the arithmetic:

$x - 1 = (x + 18) - x$

Group like terms:

$x - 1 = (x - x) + 18$

Simplify the arithmetic:

$x - 1 = 18$

Add to both sides:

$(x - 1) + 1 = 18 + 1$

Simplify the arithmetic:

$x = 18 + 1$

Simplify the arithmetic:

$x = 19$

10 additional steps

$(2 x - 1) = - (x + 18)$

Expand the parentheses:

$(2 x - 1) = - x - 18$

Add to both sides:

$(2 x - 1) + x = (- x - 18) + x$

Group like terms:

$(2 x + x) - 1 = (- x - 18) + x$

Simplify the arithmetic:

$3 x - 1 = (- x - 18) + x$

Group like terms:

$3 x - 1 = (- x + x) - 18$

Simplify the arithmetic:

$3 x - 1 = - 18$

Add to both sides:

$(3 x - 1) + 1 = - 18 + 1$

Simplify the arithmetic:

$3 x = - 18 + 1$

Simplify the arithmetic:

$3 x = - 17$

Divide both sides by :

$\frac{(3 x)}{3} = \frac{- 17}{3}$

Simplify the fraction:

$x = \frac{- 17}{3}$

3. List the solutions

$x = 19, - \frac{17}{3}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 2 x - 1 |$
$y = | x + 18 |$
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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