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Solution - Absolute value equations

Exact form:

x = - \frac{11}{3}, \frac{9}{7}

x=-\frac{11}{3} , \frac{9}{7}

Mixed number form:

x = - 3 \frac{2}{3}, 1 \frac{2}{7}

x=-3\frac{2}{3} , 1\frac{2}{7}

Decimal form:

x = - 3.667, 1.286

x=-3.667 , 1.286

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
$| 10 x + 2 | = | 4 x - 20 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 10 x + 2 \| = \| 4 x - 20 \|$
$x = + y$	$(10 x + 2) = (4 x - 20)$
$x = - y$	$(10 x + 2) = - (4 x - 20)$
$+ x = y$	$(10 x + 2) = (4 x - 20)$
$- x = y$	$- (10 x + 2) = (4 x - 20)$

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:

$\| x \| = \| y \|$	$\| 10 x + 2 \| = \| 4 x - 20 \|$
$x = + y$ , $+ x = y$	$(10 x + 2) = (4 x - 20)$
$x = - y$ , $- x = y$	$(10 x + 2) = - (4 x - 20)$

2. Solve the two equations for x

11 additional steps

$(10 x + 2) = (4 x - 20)$

Subtract from both sides:

$(10 x + 2) - 4 x = (4 x - 20) - 4 x$

Group like terms:

$(10 x - 4 x) + 2 = (4 x - 20) - 4 x$

Simplify the arithmetic:

$6 x + 2 = (4 x - 20) - 4 x$

Group like terms:

$6 x + 2 = (4 x - 4 x) - 20$

Simplify the arithmetic:

$6 x + 2 = - 20$

Subtract from both sides:

$(6 x + 2) - 2 = - 20 - 2$

Simplify the arithmetic:

$6 x = - 20 - 2$

Simplify the arithmetic:

$6 x = - 22$

Divide both sides by :

$\frac{(6 x)}{6} = \frac{- 22}{6}$

Simplify the fraction:

$x = \frac{- 22}{6}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 11 \cdot 2)}{(3 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = \frac{- 11}{3}$

12 additional steps

$(10 x + 2) = - (4 x - 20)$

Expand the parentheses:

$(10 x + 2) = - 4 x + 20$

Add to both sides:

$(10 x + 2) + 4 x = (- 4 x + 20) + 4 x$

Group like terms:

$(10 x + 4 x) + 2 = (- 4 x + 20) + 4 x$

Simplify the arithmetic:

$14 x + 2 = (- 4 x + 20) + 4 x$

Group like terms:

$14 x + 2 = (- 4 x + 4 x) + 20$

Simplify the arithmetic:

$14 x + 2 = 20$

Subtract from both sides:

$(14 x + 2) - 2 = 20 - 2$

Simplify the arithmetic:

$14 x = 20 - 2$

Simplify the arithmetic:

$14 x = 18$

Divide both sides by :

$\frac{(14 x)}{14} = \frac{18}{14}$

Simplify the fraction:

$x = \frac{18}{14}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(9 \cdot 2)}{(7 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = \frac{9}{7}$

3. List the solutions

$x = - \frac{11}{3}, \frac{9}{7}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 10 x + 2 |$
$y = | 4 x - 20 |$
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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