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Solution - Absolute value equations

Exact form:

x = - 10, \frac{2}{5}

x=-10 , \frac{2}{5}

Decimal form:

x = - 10, 0.4

x=-10 , 0.4

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
$| 3 x + 4 | = 2 | x - 3 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 3 x + 4 \| = 2 \| x - 3 \|$
$x = + y$	$(3 x + 4) = 2 (x - 3)$
$x = - y$	$(3 x + 4) = 2 (- (x - 3))$
$+ x = y$	$(3 x + 4) = 2 (x - 3)$
$- x = y$	$- (3 x + 4) = 2 (x - 3)$

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:

$\| x \| = \| y \|$	$\| 3 x + 4 \| = 2 \| x - 3 \|$
$x = + y$ , $+ x = y$	$(3 x + 4) = 2 (x - 3)$
$x = - y$ , $- x = y$	$(3 x + 4) = 2 (- (x - 3))$

2. Solve the two equations for x

9 additional steps

$(3 x + 4) = 2 \cdot (x - 3)$

Expand the parentheses:

$(3 x + 4) = 2 x + 2 \cdot - 3$

Simplify the arithmetic:

$(3 x + 4) = 2 x - 6$

Subtract from both sides:

$(3 x + 4) - 2 x = (2 x - 6) - 2 x$

Group like terms:

$(3 x - 2 x) + 4 = (2 x - 6) - 2 x$

Simplify the arithmetic:

$x + 4 = (2 x - 6) - 2 x$

Group like terms:

$x + 4 = (2 x - 2 x) - 6$

Simplify the arithmetic:

$x + 4 = - 6$

Subtract from both sides:

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

Simplify the arithmetic:

$x = - 6 - 4$

Simplify the arithmetic:

$x = - 10$

14 additional steps

$(3 x + 4) = 2 \cdot (- (x - 3))$

Expand the parentheses:

$(3 x + 4) = 2 \cdot (- x + 3)$

$(3 x + 4) = 2 \cdot - x + 2 \cdot 3$

Group like terms:

$(3 x + 4) = (2 \cdot - 1) x + 2 \cdot 3$

Multiply the coefficients:

$(3 x + 4) = - 2 x + 2 \cdot 3$

Simplify the arithmetic:

$(3 x + 4) = - 2 x + 6$

Add to both sides:

$(3 x + 4) + 2 x = (- 2 x + 6) + 2 x$

Group like terms:

$(3 x + 2 x) + 4 = (- 2 x + 6) + 2 x$

Simplify the arithmetic:

$5 x + 4 = (- 2 x + 6) + 2 x$

Group like terms:

$5 x + 4 = (- 2 x + 2 x) + 6$

Simplify the arithmetic:

$5 x + 4 = 6$

Subtract from both sides:

$(5 x + 4) - 4 = 6 - 4$

Simplify the arithmetic:

$5 x = 6 - 4$

Simplify the arithmetic:

$5 x = 2$

Divide both sides by :

$\frac{(5 x)}{5} = \frac{2}{5}$

Simplify the fraction:

$x = \frac{2}{5}$

3. List the solutions

$x = - 10, \frac{2}{5}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 3 x + 4 |$
$y = 2 | x - 3 |$
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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