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Solution - Absolute value equations

Exact form:

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

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

Mixed number form:

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

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

Decimal form:

x = - 1.5, - 3

x=-1.5 , -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
$| - 5 x - 9 | = | 3 x + 3 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 5 x - 9 \| = \| 3 x + 3 \|$
$x = + y$	$(- 5 x - 9) = (3 x + 3)$
$x = - y$	$(- 5 x - 9) = - (3 x + 3)$
$+ x = y$	$(- 5 x - 9) = (3 x + 3)$
$- x = y$	$- (- 5 x - 9) = (3 x + 3)$

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:

$\| x \| = \| y \|$	$\| - 5 x - 9 \| = \| 3 x + 3 \|$
$x = + y$ , $+ x = y$	$(- 5 x - 9) = (3 x + 3)$
$x = - y$ , $- x = y$	$(- 5 x - 9) = - (3 x + 3)$

2. Solve the two equations for x

13 additional steps

$(- 5 x - 9) = (3 x + 3)$

Subtract from both sides:

$(- 5 x - 9) - 3 x = (3 x + 3) - 3 x$

Group like terms:

$(- 5 x - 3 x) - 9 = (3 x + 3) - 3 x$

Simplify the arithmetic:

$- 8 x - 9 = (3 x + 3) - 3 x$

Group like terms:

$- 8 x - 9 = (3 x - 3 x) + 3$

Simplify the arithmetic:

$- 8 x - 9 = 3$

Add to both sides:

$(- 8 x - 9) + 9 = 3 + 9$

Simplify the arithmetic:

$- 8 x = 3 + 9$

Simplify the arithmetic:

$- 8 x = 12$

Divide both sides by :

$\frac{(- 8 x)}{- 8} = \frac{12}{- 8}$

Cancel out the negatives:

$\frac{8 x}{8} = \frac{12}{- 8}$

Simplify the fraction:

$x = \frac{12}{- 8}$

Move the negative sign from the denominator to the numerator:

$x = \frac{- 12}{8}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 3 \cdot 4)}{(2 \cdot 4)}$

Factor out and cancel the greatest common factor:

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

14 additional steps

$(- 5 x - 9) = - (3 x + 3)$

Expand the parentheses:

$(- 5 x - 9) = - 3 x - 3$

Add to both sides:

$(- 5 x - 9) + 3 x = (- 3 x - 3) + 3 x$

Group like terms:

$(- 5 x + 3 x) - 9 = (- 3 x - 3) + 3 x$

Simplify the arithmetic:

$- 2 x - 9 = (- 3 x - 3) + 3 x$

Group like terms:

$- 2 x - 9 = (- 3 x + 3 x) - 3$

Simplify the arithmetic:

$- 2 x - 9 = - 3$

Add to both sides:

$(- 2 x - 9) + 9 = - 3 + 9$

Simplify the arithmetic:

$- 2 x = - 3 + 9$

Simplify the arithmetic:

$- 2 x = 6$

Divide both sides by :

$\frac{(- 2 x)}{- 2} = \frac{6}{- 2}$

Cancel out the negatives:

$\frac{2 x}{2} = \frac{6}{- 2}$

Simplify the fraction:

$x = \frac{6}{- 2}$

Move the negative sign from the denominator to the numerator:

$x = \frac{- 6}{2}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 3 \cdot 2)}{(1 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = - 3$

3. List the solutions

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

4. Graph

Each line represents the function of one side of the equation:
$y = | - 5 x - 9 |$
$y = | 3 x + 3 |$
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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