Enter an equation or problem

Camera input is not recognized!

Solution - Absolute value equations

Exact form:

x = - 4, \frac{1}{2}

x=-4 , \frac{1}{2}

Decimal form:

x = - 4, 0.5

x=-4 , 0.5

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
$| 7 x - 8 | = | 9 x |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 7 x - 8 \| = \| 9 x \|$
$x = + y$	$(7 x - 8) = (9 x)$
$x = - y$	$(7 x - 8) = - (9 x)$
$+ x = y$	$(7 x - 8) = (9 x)$
$- x = y$	$- (7 x - 8) = (9 x)$

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:

$\| x \| = \| y \|$	$\| 7 x - 8 \| = \| 9 x \|$
$x = + y$ , $+ x = y$	$(7 x - 8) = (9 x)$
$x = - y$ , $- x = y$	$(7 x - 8) = - (9 x)$

2. Solve the two equations for x

12 additional steps

$(7 x - 8) = 9 x$

Subtract from both sides:

$(7 x - 8) - 9 x = (9 x) - 9 x$

Group like terms:

$(7 x - 9 x) - 8 = (9 x) - 9 x$

Simplify the arithmetic:

$- 2 x - 8 = (9 x) - 9 x$

Simplify the arithmetic:

$- 2 x - 8 = 0$

Add to both sides:

$(- 2 x - 8) + 8 = 0 + 8$

Simplify the arithmetic:

$- 2 x = 0 + 8$

Simplify the arithmetic:

$- 2 x = 8$

Divide both sides by :

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

Cancel out the negatives:

$\frac{2 x}{2} = \frac{8}{- 2}$

Simplify the fraction:

$x = \frac{8}{- 2}$

Move the negative sign from the denominator to the numerator:

$x = \frac{- 8}{2}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(- 4 \cdot 2)}{(1 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = - 4$

9 additional steps

$(7 x - 8) = - 9 x$

Add to both sides:

$(7 x - 8) + 8 = (- 9 x) + 8$

Simplify the arithmetic:

$7 x = (- 9 x) + 8$

Add to both sides:

$(7 x) + 9 x = ((- 9 x) + 8) + 9 x$

Simplify the arithmetic:

$16 x = ((- 9 x) + 8) + 9 x$

Group like terms:

$16 x = (- 9 x + 9 x) + 8$

Simplify the arithmetic:

$16 x = 8$

Divide both sides by :

$\frac{(16 x)}{16} = \frac{8}{16}$

Simplify the fraction:

$x = \frac{8}{16}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(1 \cdot 8)}{(2 \cdot 8)}$

Factor out and cancel the greatest common factor:

$x = \frac{1}{2}$

3. List the solutions

$x = - 4, \frac{1}{2}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 7 x - 8 |$
$y = | 9 x |$
The equation is true where the two lines cross.

How did we do?

Please leave us feedback.

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

Latest Related Drills Solved