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Solution - Absolute value equations

Exact form:

x = 15, - 1

x=15 , -1

See steps

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

$| 2 x - 6 | - | x + 9 | = 0$

Add $| x + 9 |$ to both sides of the equation:

$| 2 x - 6 | - | x + 9 | + | x + 9 | = | x + 9 |$

Simplify the arithmetic

$| 2 x - 6 | = | x + 9 |$

2. 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
$| 2 x - 6 | = | x + 9 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 2 x - 6 \| = \| x + 9 \|$
$x = + y$	$(2 x - 6) = (x + 9)$
$x = - y$	$(2 x - 6) = (- (x + 9))$
$+ x = y$	$(2 x - 6) = (x + 9)$
$- x = y$	$- (2 x - 6) = (x + 9)$

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:

$\| x \| = \| y \|$	$\| 2 x - 6 \| = \| x + 9 \|$
$x = + y$ , $+ x = y$	$(2 x - 6) = (x + 9)$
$x = - y$ , $- x = y$	$(2 x - 6) = (- (x + 9))$

3. Solve the two equations for x

7 additional steps

$(2 x - 6) = (x + 9)$

Subtract from both sides:

$(2 x - 6) - x = (x + 9) - x$

Group like terms:

$(2 x - x) - 6 = (x + 9) - x$

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

$x - 6 = 9$

Add to both sides:

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

Simplify the arithmetic:

$x = 9 + 6$

Simplify the arithmetic:

$x = 15$

11 additional steps

$(2 x - 6) = - (x + 9)$

Expand the parentheses:

$(2 x - 6) = - x - 9$

Add to both sides:

$(2 x - 6) + x = (- x - 9) + x$

Group like terms:

$(2 x + x) - 6 = (- x - 9) + x$

Simplify the arithmetic:

$3 x - 6 = (- x - 9) + x$

Group like terms:

$3 x - 6 = (- x + x) - 9$

Simplify the arithmetic:

$3 x - 6 = - 9$

Add to both sides:

$(3 x - 6) + 6 = - 9 + 6$

Simplify the arithmetic:

$3 x = - 9 + 6$

Simplify the arithmetic:

$3 x = - 3$

Divide both sides by :

$\frac{(3 x)}{3} = \frac{- 3}{3}$

Simplify the fraction:

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

Simplify the fraction:

$x = - 1$

4. List the solutions

$x = 15, - 1$
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
$y = | 2 x - 6 |$
$y = | x + 9 |$
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 with one absolute value terms on each side

2. Rewrite the equation without absolute value bars

3. Solve the two equations for x

4. List the solutions

5. Graph

Why learn this

Terms and topics

Related links

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

2. Rewrite the equation without absolute value bars

3. Solve the two equations for x

4. List the solutions

5. Graph

Why learn this

Terms and topics

Related links

Latest Related Drills Solved