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Solution - Absolute value equations

Exact form:

x = 3

x=3

See steps

Step-by-step explanation

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

$| x + 3 | + | x - 9 | = 0$

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

$| x + 3 | + | x - 9 | - | x - 9 | = - | x - 9 |$

Simplify the arithmetic

$| x + 3 | = - | x - 9 |$

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
$| x + 3 | = - | x - 9 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| x + 3 \| = - \| x - 9 \|$
$x = + y$	$(x + 3) = - (x - 9)$
$x = - y$	$(x + 3) = - - (x - 9)$
$+ x = y$	$(x + 3) = - (x - 9)$
$- x = y$	$- (x + 3) = - (x - 9)$

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:

$\| x \| = \| y \|$	$\| x + 3 \| = - \| x - 9 \|$
$x = + y$ , $+ x = y$	$(x + 3) = - (x - 9)$
$x = - y$ , $- x = y$	$(x + 3) = - - (x - 9)$

3. Solve the two equations for x

12 additional steps

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

Expand the parentheses:

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

$2 x + 3 = (- x + 9) + x$

Group like terms:

$2 x + 3 = (- x + x) + 9$

Simplify the arithmetic:

$2 x + 3 = 9$

Subtract from both sides:

$(2 x + 3) - 3 = 9 - 3$

Simplify the arithmetic:

$2 x = 9 - 3$

Simplify the arithmetic:

$2 x = 6$

Divide both sides by :

$\frac{(2 x)}{2} = \frac{6}{2}$

Simplify the fraction:

$x = \frac{6}{2}$

Find the greatest common factor of the numerator and denominator:

$x = \frac{(3 \cdot 2)}{(1 \cdot 2)}$

Factor out and cancel the greatest common factor:

$x = 3$

6 additional steps

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

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

$(x + 3) = x - 9$

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

$3 = (x - 9) - x$

Group like terms:

$3 = (x - x) - 9$

Simplify the arithmetic:

$3 = - 9$

The statement is false:

$3 = - 9$

The equation is false so it has no solution.

4. List the solutions

$x = 3$
(1 solution(s))

5. Graph

Each line represents the function of one side of the equation:
$y = | x + 3 |$
$y = - | x - 9 |$
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