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Solution - Absolute value equations

Exact form:

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

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

Decimal form:

x = 1, - 0.667

x=1 , -0.667

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
$| 20 x | = | 4 x + 16 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 20 x \| = \| 4 x + 16 \|$
$x = + y$	$(20 x) = (4 x + 16)$
$x = - y$	$(20 x) = - (4 x + 16)$
$+ x = y$	$(20 x) = (4 x + 16)$
$- x = y$	$- (20 x) = (4 x + 16)$

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:

$\| x \| = \| y \|$	$\| 20 x \| = \| 4 x + 16 \|$
$x = + y$ , $+ x = y$	$(20 x) = (4 x + 16)$
$x = - y$ , $- x = y$	$(20 x) = - (4 x + 16)$

2. Solve the two equations for x

6 additional steps

$20 x = (4 x + 16)$

Subtract from both sides:

$(20 x) - 4 x = (4 x + 16) - 4 x$

Simplify the arithmetic:

$16 x = (4 x + 16) - 4 x$

Group like terms:

$16 x = (4 x - 4 x) + 16$

Simplify the arithmetic:

$16 x = 16$

Divide both sides by :

$\frac{(16 x)}{16} = \frac{16}{16}$

Simplify the fraction:

$x = \frac{16}{16}$

Simplify the fraction:

$x = 1$

8 additional steps

$20 x = - (4 x + 16)$

Expand the parentheses:

$20 x = - 4 x - 16$

Add to both sides:

$(20 x) + 4 x = (- 4 x - 16) + 4 x$

Simplify the arithmetic:

$24 x = (- 4 x - 16) + 4 x$

Group like terms:

$24 x = (- 4 x + 4 x) - 16$

Simplify the arithmetic:

$24 x = - 16$

Divide both sides by :

$\frac{(24 x)}{24} = \frac{- 16}{24}$

Simplify the fraction:

$x = \frac{- 16}{24}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 2 \cdot 8)}{(3 \cdot 8)}$

Factor out and cancel the greatest common factor:

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

3. List the solutions

$x = 1, - \frac{2}{3}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 20 x |$
$y = | 4 x + 16 |$
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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