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Solution - Absolute value equations

Exact form:

x = \frac{5}{6}, - \frac{1}{8}

x=\frac{5}{6} , -\frac{1}{8}

Decimal form:

x = 0.833, - 0.125

x=0.833 , -0.125

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
$| 7 x - 2 | = | x + 3 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 7 x - 2 \| = \| x + 3 \|$
$x = + y$	$(7 x - 2) = (x + 3)$
$x = - y$	$(7 x - 2) = - (x + 3)$
$+ x = y$	$(7 x - 2) = (x + 3)$
$- x = y$	$- (7 x - 2) = (x + 3)$

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:

$\| x \| = \| y \|$	$\| 7 x - 2 \| = \| x + 3 \|$
$x = + y$ , $+ x = y$	$(7 x - 2) = (x + 3)$
$x = - y$ , $- x = y$	$(7 x - 2) = - (x + 3)$

2. Solve the two equations for x

9 additional steps

$(7 x - 2) = (x + 3)$

Subtract from both sides:

$(7 x - 2) - x = (x + 3) - x$

Group like terms:

$(7 x - x) - 2 = (x + 3) - x$

Simplify the arithmetic:

$6 x - 2 = (x + 3) - x$

Group like terms:

$6 x - 2 = (x - x) + 3$

Simplify the arithmetic:

$6 x - 2 = 3$

Add to both sides:

$(6 x - 2) + 2 = 3 + 2$

Simplify the arithmetic:

$6 x = 3 + 2$

Simplify the arithmetic:

$6 x = 5$

Divide both sides by :

$\frac{(6 x)}{6} = \frac{5}{6}$

Simplify the fraction:

$x = \frac{5}{6}$

10 additional steps

$(7 x - 2) = - (x + 3)$

Expand the parentheses:

$(7 x - 2) = - x - 3$

Add to both sides:

$(7 x - 2) + x = (- x - 3) + x$

Group like terms:

$(7 x + x) - 2 = (- x - 3) + x$

Simplify the arithmetic:

$8 x - 2 = (- x - 3) + x$

Group like terms:

$8 x - 2 = (- x + x) - 3$

Simplify the arithmetic:

$8 x - 2 = - 3$

Add to both sides:

$(8 x - 2) + 2 = - 3 + 2$

Simplify the arithmetic:

$8 x = - 3 + 2$

Simplify the arithmetic:

$8 x = - 1$

Divide both sides by :

$\frac{(8 x)}{8} = \frac{- 1}{8}$

Simplify the fraction:

$x = \frac{- 1}{8}$

3. List the solutions

$x = \frac{5}{6}, - \frac{1}{8}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 7 x - 2 |$
$y = | x + 3 |$
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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