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Solution - Absolute value equations

Exact form:

x = \frac{3}{4}, 3

x=\frac{3}{4} , 3

Decimal form:

x = 0.75, 3

x=0.75 , 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
$| - 7 x + 12 | = | x + 6 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 7 x + 12 \| = \| x + 6 \|$
$x = + y$	$(- 7 x + 12) = (x + 6)$
$x = - y$	$(- 7 x + 12) = - (x + 6)$
$+ x = y$	$(- 7 x + 12) = (x + 6)$
$- x = y$	$- (- 7 x + 12) = (x + 6)$

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:

$\| x \| = \| y \|$	$\| - 7 x + 12 \| = \| x + 6 \|$
$x = + y$ , $+ x = y$	$(- 7 x + 12) = (x + 6)$
$x = - y$ , $- x = y$	$(- 7 x + 12) = - (x + 6)$

2. Solve the two equations for x

13 additional steps

$(- 7 x + 12) = (x + 6)$

Subtract from both sides:

$(- 7 x + 12) - x = (x + 6) - x$

Group like terms:

$(- 7 x - x) + 12 = (x + 6) - x$

Simplify the arithmetic:

$- 8 x + 12 = (x + 6) - x$

Group like terms:

$- 8 x + 12 = (x - x) + 6$

Simplify the arithmetic:

$- 8 x + 12 = 6$

Subtract from both sides:

$(- 8 x + 12) - 12 = 6 - 12$

Simplify the arithmetic:

$- 8 x = 6 - 12$

Simplify the arithmetic:

$- 8 x = - 6$

Divide both sides by :

$\frac{(- 8 x)}{- 8} = \frac{- 6}{- 8}$

Cancel out the negatives:

$\frac{8 x}{8} = \frac{- 6}{- 8}$

Simplify the fraction:

$x = \frac{- 6}{- 8}$

Cancel out the negatives:

$x = \frac{6}{8}$

Find the greatest common factor of the numerator and denominator:

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

Factor out and cancel the greatest common factor:

$x = \frac{3}{4}$

14 additional steps

$(- 7 x + 12) = - (x + 6)$

Expand the parentheses:

$(- 7 x + 12) = - x - 6$

Add to both sides:

$(- 7 x + 12) + x = (- x - 6) + x$

Group like terms:

$(- 7 x + x) + 12 = (- x - 6) + x$

Simplify the arithmetic:

$- 6 x + 12 = (- x - 6) + x$

Group like terms:

$- 6 x + 12 = (- x + x) - 6$

Simplify the arithmetic:

$- 6 x + 12 = - 6$

Subtract from both sides:

$(- 6 x + 12) - 12 = - 6 - 12$

Simplify the arithmetic:

$- 6 x = - 6 - 12$

Simplify the arithmetic:

$- 6 x = - 18$

Divide both sides by :

$\frac{(- 6 x)}{- 6} = \frac{- 18}{- 6}$

Cancel out the negatives:

$\frac{6 x}{6} = \frac{- 18}{- 6}$

Simplify the fraction:

$x = \frac{- 18}{- 6}$

Cancel out the negatives:

$x = \frac{18}{6}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(3 \cdot 6)}{(1 \cdot 6)}$

Factor out and cancel the greatest common factor:

$x = 3$

3. List the solutions

$x = \frac{3}{4}, 3$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | - 7 x + 12 |$
$y = | x + 6 |$
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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