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Solution - Absolute value equations

Exact form:

x = \frac{1}{2}, - \frac{2}{3}

x=\frac{1}{2} , -\frac{2}{3}

Decimal form:

x = 0.5, - 0.667

x=0.5 , -0.667

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
$| - 5 x - 1 | = | - x - 3 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 5 x - 1 \| = \| - x - 3 \|$
$x = + y$	$(- 5 x - 1) = (- x - 3)$
$x = - y$	$(- 5 x - 1) = - (- x - 3)$
$+ x = y$	$(- 5 x - 1) = (- x - 3)$
$- x = y$	$- (- 5 x - 1) = (- x - 3)$

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:

$\| x \| = \| y \|$	$\| - 5 x - 1 \| = \| - x - 3 \|$
$x = + y$ , $+ x = y$	$(- 5 x - 1) = (- x - 3)$
$x = - y$ , $- x = y$	$(- 5 x - 1) = - (- x - 3)$

2. Solve the two equations for x

13 additional steps

$(- 5 x - 1) = (- x - 3)$

Add to both sides:

$(- 5 x - 1) + x = (- x - 3) + x$

Group like terms:

$(- 5 x + x) - 1 = (- x - 3) + x$

Simplify the arithmetic:

$- 4 x - 1 = (- x - 3) + x$

Group like terms:

$- 4 x - 1 = (- x + x) - 3$

Simplify the arithmetic:

$- 4 x - 1 = - 3$

Add to both sides:

$(- 4 x - 1) + 1 = - 3 + 1$

Simplify the arithmetic:

$- 4 x = - 3 + 1$

Simplify the arithmetic:

$- 4 x = - 2$

Divide both sides by :

$\frac{(- 4 x)}{- 4} = \frac{- 2}{- 4}$

Cancel out the negatives:

$\frac{4 x}{4} = \frac{- 2}{- 4}$

Simplify the fraction:

$x = \frac{- 2}{- 4}$

Cancel out the negatives:

$x = \frac{2}{4}$

Find the greatest common factor of the numerator and denominator:

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

Factor out and cancel the greatest common factor:

$x = \frac{1}{2}$

14 additional steps

$(- 5 x - 1) = - (- x - 3)$

Expand the parentheses:

$(- 5 x - 1) = x + 3$

Subtract from both sides:

$(- 5 x - 1) - x = (x + 3) - x$

Group like terms:

$(- 5 x - x) - 1 = (x + 3) - x$

Simplify the arithmetic:

$- 6 x - 1 = (x + 3) - x$

Group like terms:

$- 6 x - 1 = (x - x) + 3$

Simplify the arithmetic:

$- 6 x - 1 = 3$

Add to both sides:

$(- 6 x - 1) + 1 = 3 + 1$

Simplify the arithmetic:

$- 6 x = 3 + 1$

Simplify the arithmetic:

$- 6 x = 4$

Divide both sides by :

$\frac{(- 6 x)}{- 6} = \frac{4}{- 6}$

Cancel out the negatives:

$\frac{6 x}{6} = \frac{4}{- 6}$

Simplify the fraction:

$x = \frac{4}{- 6}$

Move the negative sign from the denominator to the numerator:

$x = \frac{- 4}{6}$

Find the greatest common factor of the numerator and denominator:

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

Factor out and cancel the greatest common factor:

$x = \frac{- 2}{3}$

3. List the solutions

$x = \frac{1}{2}, - \frac{2}{3}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | - 5 x - 1 |$
$y = | - x - 3 |$
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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