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Solution - Absolute value equations

Exact form:

x = 3

x=3

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
$| - 4 x - 5 | = | 4 x - 29 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 4 x - 5 \| = \| 4 x - 29 \|$
$x = + y$	$(- 4 x - 5) = (4 x - 29)$
$x = - y$	$(- 4 x - 5) = - (4 x - 29)$
$+ x = y$	$(- 4 x - 5) = (4 x - 29)$
$- x = y$	$- (- 4 x - 5) = (4 x - 29)$

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:

$\| x \| = \| y \|$	$\| - 4 x - 5 \| = \| 4 x - 29 \|$
$x = + y$ , $+ x = y$	$(- 4 x - 5) = (4 x - 29)$
$x = - y$ , $- x = y$	$(- 4 x - 5) = - (4 x - 29)$

2. Solve the two equations for x

13 additional steps

$(- 4 x - 5) = (4 x - 29)$

Subtract from both sides:

$(- 4 x - 5) - 4 x = (4 x - 29) - 4 x$

Group like terms:

$(- 4 x - 4 x) - 5 = (4 x - 29) - 4 x$

Simplify the arithmetic:

$- 8 x - 5 = (4 x - 29) - 4 x$

Group like terms:

$- 8 x - 5 = (4 x - 4 x) - 29$

Simplify the arithmetic:

$- 8 x - 5 = - 29$

Add to both sides:

$(- 8 x - 5) + 5 = - 29 + 5$

Simplify the arithmetic:

$- 8 x = - 29 + 5$

Simplify the arithmetic:

$- 8 x = - 24$

Divide both sides by :

$\frac{(- 8 x)}{- 8} = \frac{- 24}{- 8}$

Cancel out the negatives:

$\frac{8 x}{8} = \frac{- 24}{- 8}$

Simplify the fraction:

$x = \frac{- 24}{- 8}$

Cancel out the negatives:

$x = \frac{24}{8}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(3 \cdot 8)}{(1 \cdot 8)}$

Factor out and cancel the greatest common factor:

$x = 3$

6 additional steps

$(- 4 x - 5) = - (4 x - 29)$

Expand the parentheses:

$(- 4 x - 5) = - 4 x + 29$

Add to both sides:

$(- 4 x - 5) + 4 x = (- 4 x + 29) + 4 x$

Group like terms:

$(- 4 x + 4 x) - 5 = (- 4 x + 29) + 4 x$

Simplify the arithmetic:

$- 5 = (- 4 x + 29) + 4 x$

Group like terms:

$- 5 = (- 4 x + 4 x) + 29$

Simplify the arithmetic:

$- 5 = 29$

The statement is false:

$- 5 = 29$

The equation is false so it has no solution.

3. List the solutions

$x = 3$
(1 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | - 4 x - 5 |$
$y = | 4 x - 29 |$
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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