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Solution - Absolute value equations

Exact form:

x = 0, 0

x=0 , 0

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
$| - 3 x | = | 7 x |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| - 3 x \| = \| 7 x \|$
$x = + y$	$(- 3 x) = (7 x)$
$x = - y$	$(- 3 x) = - (7 x)$
$+ x = y$	$(- 3 x) = (7 x)$
$- x = y$	$- (- 3 x) = (7 x)$

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:

$\| x \| = \| y \|$	$\| - 3 x \| = \| 7 x \|$
$x = + y$ , $+ x = y$	$(- 3 x) = (7 x)$
$x = - y$ , $- x = y$	$(- 3 x) = - (7 x)$

2. Solve the two equations for x

3 additional steps

$(- 3 x) = 7 x$

Subtract from both sides:

$(- 3 x) - 7 x = (7 x) - 7 x$

Simplify the arithmetic:

$- 10 x = (7 x) - 7 x$

Simplify the arithmetic:

$- 10 x = 0$

Divide both sides by the coefficient:

$x = 0$

13 additional steps

$(- 3 x) = - 7 x$

Divide both sides by :

$\frac{(- 3 x)}{- 3} = \frac{(- 7 x)}{- 3}$

Cancel out the negatives:

$\frac{3 x}{3} = \frac{(- 7 x)}{- 3}$

Simplify the fraction:

$x = \frac{(- 7 x)}{- 3}$

Cancel out the negatives:

$x = \frac{7 x}{3}$

Subtract from both sides:

$x - \frac{7 x}{3} = (\frac{7 x}{3}) - \frac{7 x}{3}$

Group the coefficients:

$(1 + \frac{- 7}{3}) x = (\frac{7 x}{3}) - \frac{7 x}{3}$

Convert the integer into a fraction:

$(\frac{3}{3} + \frac{- 7}{3}) x = (\frac{7 x}{3}) - \frac{7 x}{3}$

Combine the fractions:

$\frac{(3 - 7)}{3} x = (\frac{7 x}{3}) - \frac{7 x}{3}$

Combine the numerators:

$\frac{- 4}{3} x = (\frac{7 x}{3}) - \frac{7 x}{3}$

Combine the fractions:

$\frac{- 4}{3} \cdot x = \frac{(7 - 7)}{3} x$

Combine the numerators:

$\frac{- 4}{3} \cdot x = \frac{0}{3} x$

Reduce the zero numerator:

$\frac{- 4}{3} x = 0 x$

Simplify the arithmetic:

$\frac{- 4}{3} x = 0$

Divide both sides by the coefficient:

$x = 0$

3. List the solutions

$x = 0, 0$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | - 3 x |$
$y = | 7 x |$
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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