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Solution - Absolute value equations

Exact form:

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

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

Decimal form:

x = 2, - 0.667

x=2 , -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
$| 7 x + 6 | = | 8 x + 4 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 7 x + 6 \| = \| 8 x + 4 \|$
$x = + y$	$(7 x + 6) = (8 x + 4)$
$x = - y$	$(7 x + 6) = - (8 x + 4)$
$+ x = y$	$(7 x + 6) = (8 x + 4)$
$- x = y$	$- (7 x + 6) = (8 x + 4)$

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:

$\| x \| = \| y \|$	$\| 7 x + 6 \| = \| 8 x + 4 \|$
$x = + y$ , $+ x = y$	$(7 x + 6) = (8 x + 4)$
$x = - y$ , $- x = y$	$(7 x + 6) = - (8 x + 4)$

2. Solve the two equations for x

10 additional steps

$(7 x + 6) = (8 x + 4)$

Subtract from both sides:

$(7 x + 6) - 8 x = (8 x + 4) - 8 x$

Group like terms:

$(7 x - 8 x) + 6 = (8 x + 4) - 8 x$

Simplify the arithmetic:

$- x + 6 = (8 x + 4) - 8 x$

Group like terms:

$- x + 6 = (8 x - 8 x) + 4$

Simplify the arithmetic:

$- x + 6 = 4$

Subtract from both sides:

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

Simplify the arithmetic:

$- x = 4 - 6$

Simplify the arithmetic:

$- x = - 2$

Multiply both sides by :

$- x \cdot - 1 = - 2 \cdot - 1$

Remove the one(s):

$x = - 2 \cdot - 1$

Simplify the arithmetic:

$x = 2$

12 additional steps

$(7 x + 6) = - (8 x + 4)$

Expand the parentheses:

$(7 x + 6) = - 8 x - 4$

Add to both sides:

$(7 x + 6) + 8 x = (- 8 x - 4) + 8 x$

Group like terms:

$(7 x + 8 x) + 6 = (- 8 x - 4) + 8 x$

Simplify the arithmetic:

$15 x + 6 = (- 8 x - 4) + 8 x$

Group like terms:

$15 x + 6 = (- 8 x + 8 x) - 4$

Simplify the arithmetic:

$15 x + 6 = - 4$

Subtract from both sides:

$(15 x + 6) - 6 = - 4 - 6$

Simplify the arithmetic:

$15 x = - 4 - 6$

Simplify the arithmetic:

$15 x = - 10$

Divide both sides by :

$\frac{(15 x)}{15} = \frac{- 10}{15}$

Simplify the fraction:

$x = \frac{- 10}{15}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 2 \cdot 5)}{(3 \cdot 5)}$

Factor out and cancel the greatest common factor:

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

3. List the solutions

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

4. Graph

Each line represents the function of one side of the equation:
$y = | 7 x + 6 |$
$y = | 8 x + 4 |$
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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