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Solution - Absolute value equations

Exact form:

x = 0, - \frac{8}{9}

x=0 , -\frac{8}{9}

Decimal form:

x = 0, - 0.889

x=0 , -0.889

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
$| 3 x + 4 | = | 6 x + 4 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 3 x + 4 \| = \| 6 x + 4 \|$
$x = + y$	$(3 x + 4) = (6 x + 4)$
$x = - y$	$(3 x + 4) = - (6 x + 4)$
$+ x = y$	$(3 x + 4) = (6 x + 4)$
$- x = y$	$- (3 x + 4) = (6 x + 4)$

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:

$\| x \| = \| y \|$	$\| 3 x + 4 \| = \| 6 x + 4 \|$
$x = + y$ , $+ x = y$	$(3 x + 4) = (6 x + 4)$
$x = - y$ , $- x = y$	$(3 x + 4) = - (6 x + 4)$

2. Solve the two equations for x

8 additional steps

$(3 x + 4) = (6 x + 4)$

Subtract from both sides:

$(3 x + 4) - 6 x = (6 x + 4) - 6 x$

Group like terms:

$(3 x - 6 x) + 4 = (6 x + 4) - 6 x$

Simplify the arithmetic:

$- 3 x + 4 = (6 x + 4) - 6 x$

Group like terms:

$- 3 x + 4 = (6 x - 6 x) + 4$

Simplify the arithmetic:

$- 3 x + 4 = 4$

Subtract from both sides:

$(- 3 x + 4) - 4 = 4 - 4$

Simplify the arithmetic:

$- 3 x = 4 - 4$

Simplify the arithmetic:

$- 3 x = 0$

Divide both sides by the coefficient:

$x = 0$

10 additional steps

$(3 x + 4) = - (6 x + 4)$

Expand the parentheses:

$(3 x + 4) = - 6 x - 4$

Add to both sides:

$(3 x + 4) + 6 x = (- 6 x - 4) + 6 x$

Group like terms:

$(3 x + 6 x) + 4 = (- 6 x - 4) + 6 x$

Simplify the arithmetic:

$9 x + 4 = (- 6 x - 4) + 6 x$

Group like terms:

$9 x + 4 = (- 6 x + 6 x) - 4$

Simplify the arithmetic:

$9 x + 4 = - 4$

Subtract from both sides:

$(9 x + 4) - 4 = - 4 - 4$

Simplify the arithmetic:

$9 x = - 4 - 4$

Simplify the arithmetic:

$9 x = - 8$

Divide both sides by :

$\frac{(9 x)}{9} = \frac{- 8}{9}$

Simplify the fraction:

$x = \frac{- 8}{9}$

3. List the solutions

$x = 0, - \frac{8}{9}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 3 x + 4 |$
$y = | 6 x + 4 |$
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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