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Solution - Absolute value equations

Exact form:

k = \frac{2}{9}, \frac{2}{17}

k=\frac{2}{9} , \frac{2}{17}

Decimal form:

k = 0.222, 0.118

k=0.222 , 0.118

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
$| 4 k | = | 13 k - 2 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 4 k \| = \| 13 k - 2 \|$
$x = + y$	$(4 k) = (13 k - 2)$
$x = - y$	$(4 k) = - (13 k - 2)$
$+ x = y$	$(4 k) = (13 k - 2)$
$- x = y$	$- (4 k) = (13 k - 2)$

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:

$\| x \| = \| y \|$	$\| 4 k \| = \| 13 k - 2 \|$
$x = + y$ , $+ x = y$	$(4 k) = (13 k - 2)$
$x = - y$ , $- x = y$	$(4 k) = - (13 k - 2)$

2. Solve the two equations for k

7 additional steps

$4 k = (13 k - 2)$

Subtract from both sides:

$(4 k) - 13 k = (13 k - 2) - 13 k$

Simplify the arithmetic:

$- 9 k = (13 k - 2) - 13 k$

Group like terms:

$- 9 k = (13 k - 13 k) - 2$

Simplify the arithmetic:

$- 9 k = - 2$

Divide both sides by :

$\frac{(- 9 k)}{- 9} = \frac{- 2}{- 9}$

Cancel out the negatives:

$\frac{9 k}{9} = \frac{- 2}{- 9}$

Simplify the fraction:

$k = \frac{- 2}{- 9}$

Cancel out the negatives:

$k = \frac{2}{9}$

6 additional steps

$4 k = - (13 k - 2)$

Expand the parentheses:

$4 k = - 13 k + 2$

Add to both sides:

$(4 k) + 13 k = (- 13 k + 2) + 13 k$

Simplify the arithmetic:

$17 k = (- 13 k + 2) + 13 k$

Group like terms:

$17 k = (- 13 k + 13 k) + 2$

Simplify the arithmetic:

$17 k = 2$

Divide both sides by :

$\frac{(17 k)}{17} = \frac{2}{17}$

Simplify the fraction:

$k = \frac{2}{17}$

3. List the solutions

$k = \frac{2}{9}, \frac{2}{17}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 4 k |$
$y = | 13 k - 2 |$
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 k

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 k

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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