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Solution - Absolute value equations

Exact form:

x = 3, - \frac{4}{11}

x=3 , -\frac{4}{11}

Decimal form:

x = 3, - 0.364

x=3 , -0.364

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
$| 15 x - 8 | = | 7 x + 16 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 15 x - 8 \| = \| 7 x + 16 \|$
$x = + y$	$(15 x - 8) = (7 x + 16)$
$x = - y$	$(15 x - 8) = - (7 x + 16)$
$+ x = y$	$(15 x - 8) = (7 x + 16)$
$- x = y$	$- (15 x - 8) = (7 x + 16)$

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:

$\| x \| = \| y \|$	$\| 15 x - 8 \| = \| 7 x + 16 \|$
$x = + y$ , $+ x = y$	$(15 x - 8) = (7 x + 16)$
$x = - y$ , $- x = y$	$(15 x - 8) = - (7 x + 16)$

2. Solve the two equations for x

11 additional steps

$(15 x - 8) = (7 x + 16)$

Subtract from both sides:

$(15 x - 8) - 7 x = (7 x + 16) - 7 x$

Group like terms:

$(15 x - 7 x) - 8 = (7 x + 16) - 7 x$

Simplify the arithmetic:

$8 x - 8 = (7 x + 16) - 7 x$

Group like terms:

$8 x - 8 = (7 x - 7 x) + 16$

Simplify the arithmetic:

$8 x - 8 = 16$

Add to both sides:

$(8 x - 8) + 8 = 16 + 8$

Simplify the arithmetic:

$8 x = 16 + 8$

Simplify the arithmetic:

$8 x = 24$

Divide both sides by :

$\frac{(8 x)}{8} = \frac{24}{8}$

Simplify the fraction:

$x = \frac{24}{8}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(3 \cdot 8)}{(1 \cdot 8)}$

Factor out and cancel the greatest common factor:

$x = 3$

12 additional steps

$(15 x - 8) = - (7 x + 16)$

Expand the parentheses:

$(15 x - 8) = - 7 x - 16$

Add to both sides:

$(15 x - 8) + 7 x = (- 7 x - 16) + 7 x$

Group like terms:

$(15 x + 7 x) - 8 = (- 7 x - 16) + 7 x$

Simplify the arithmetic:

$22 x - 8 = (- 7 x - 16) + 7 x$

Group like terms:

$22 x - 8 = (- 7 x + 7 x) - 16$

Simplify the arithmetic:

$22 x - 8 = - 16$

Add to both sides:

$(22 x - 8) + 8 = - 16 + 8$

Simplify the arithmetic:

$22 x = - 16 + 8$

Simplify the arithmetic:

$22 x = - 8$

Divide both sides by :

$\frac{(22 x)}{22} = \frac{- 8}{22}$

Simplify the fraction:

$x = \frac{- 8}{22}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 4 \cdot 2)}{(11 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = \frac{- 4}{11}$

3. List the solutions

$x = 3, - \frac{4}{11}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 15 x - 8 |$
$y = | 7 x + 16 |$
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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