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Solution - Absolute value equations

Exact form:

x = - \frac{2}{3}, 8

x=-\frac{2}{3} , 8

Decimal form:

x = - 0.667, 8

x=-0.667 , 8

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
$| - 2 x + 3 | = | x + 5 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 2 x + 3 \| = \| x + 5 \|$
$x = + y$	$(- 2 x + 3) = (x + 5)$
$x = - y$	$(- 2 x + 3) = - (x + 5)$
$+ x = y$	$(- 2 x + 3) = (x + 5)$
$- x = y$	$- (- 2 x + 3) = (x + 5)$

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:

$\| x \| = \| y \|$	$\| - 2 x + 3 \| = \| x + 5 \|$
$x = + y$ , $+ x = y$	$(- 2 x + 3) = (x + 5)$
$x = - y$ , $- x = y$	$(- 2 x + 3) = - (x + 5)$

2. Solve the two equations for x

11 additional steps

$(- 2 x + 3) = (x + 5)$

Subtract from both sides:

$(- 2 x + 3) - x = (x + 5) - x$

Group like terms:

$(- 2 x - x) + 3 = (x + 5) - x$

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

$- 3 x + 3 = 5$

Subtract from both sides:

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

Simplify the arithmetic:

$- 3 x = 5 - 3$

Simplify the arithmetic:

$- 3 x = 2$

Divide both sides by :

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

Cancel out the negatives:

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

Simplify the fraction:

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

Move the negative sign from the denominator to the numerator:

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

11 additional steps

$(- 2 x + 3) = - (x + 5)$

Expand the parentheses:

$(- 2 x + 3) = - x - 5$

Add to both sides:

$(- 2 x + 3) + x = (- x - 5) + x$

Group like terms:

$(- 2 x + x) + 3 = (- x - 5) + x$

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

$- x + 3 = - 5$

Subtract from both sides:

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

Simplify the arithmetic:

$- x = - 5 - 3$

Simplify the arithmetic:

$- x = - 8$

Multiply both sides by :

$- x \cdot - 1 = - 8 \cdot - 1$

Remove the one(s):

$x = - 8 \cdot - 1$

Simplify the arithmetic:

$x = 8$

3. List the solutions

$x = - \frac{2}{3}, 8$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | - 2 x + 3 |$
$y = | x + 5 |$
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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