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Solution - Absolute value equations

Exact form:

k = 4

k=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
$| k - 8 | = | k |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| k - 8 \| = \| k \|$
$x = + y$	$(k - 8) = (k)$
$x = - y$	$(k - 8) = - (k)$
$+ x = y$	$(k - 8) = (k)$
$- x = y$	$- (k - 8) = (k)$

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:

$\| x \| = \| y \|$	$\| k - 8 \| = \| k \|$
$x = + y$ , $+ x = y$	$(k - 8) = (k)$
$x = - y$ , $- x = y$	$(k - 8) = - (k)$

2. Solve the two equations for k

4 additional steps

$(k - 8) = k$

Subtract from both sides:

$(k - 8) - k = k - k$

Group like terms:

$(k - k) - 8 = k - k$

Simplify the arithmetic:

$- 8 = k - k$

Simplify the arithmetic:

$- 8 = 0$

The statement is false:

$- 8 = 0$

The equation is false so it has no solution.

10 additional steps

$(k - 8) = - k$

Add to both sides:

$(k - 8) + k = - k + k$

Group like terms:

$(k + k) - 8 = - k + k$

Simplify the arithmetic:

$2 k - 8 = - k + k$

Simplify the arithmetic:

$2 k - 8 = 0$

Add to both sides:

$(2 k - 8) + 8 = 0 + 8$

Simplify the arithmetic:

$2 k = 0 + 8$

Simplify the arithmetic:

$2 k = 8$

Divide both sides by :

$\frac{(2 k)}{2} = \frac{8}{2}$

Simplify the fraction:

$k = \frac{8}{2}$

Find the greatest common factor of the numerator and denominator:

$k = \frac{(4 \cdot 2)}{(1 \cdot 2)}$

Factor out and cancel the greatest common factor:

$k = 4$

3. Graph

Each line represents the function of one side of the equation:
$y = | k - 8 |$
$y = | k |$
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. 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. Graph

Why learn this

Terms and topics

Related links

Latest Related Drills Solved