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Solution - Absolute value equations

Exact form:

q = - \frac{9}{2}, - \frac{7}{6}

q=-\frac{9}{2} , -\frac{7}{6}

Mixed number form:

q = - 4 \frac{1}{2}, - 1 \frac{1}{6}

q=-4\frac{1}{2} , -1\frac{1}{6}

Decimal form:

q = - 4.5, - 1.167

q=-4.5 , -1.167

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
$| 4 q + 8 | = | 2 q - 1 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 4 q + 8 \| = \| 2 q - 1 \|$
$x = + y$	$(4 q + 8) = (2 q - 1)$
$x = - y$	$(4 q + 8) = - (2 q - 1)$
$+ x = y$	$(4 q + 8) = (2 q - 1)$
$- x = y$	$- (4 q + 8) = (2 q - 1)$

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:

$\| x \| = \| y \|$	$\| 4 q + 8 \| = \| 2 q - 1 \|$
$x = + y$ , $+ x = y$	$(4 q + 8) = (2 q - 1)$
$x = - y$ , $- x = y$	$(4 q + 8) = - (2 q - 1)$

2. Solve the two equations for q

9 additional steps

$(4 q + 8) = (2 q - 1)$

Subtract from both sides:

$(4 q + 8) - 2 q = (2 q - 1) - 2 q$

Group like terms:

$(4 q - 2 q) + 8 = (2 q - 1) - 2 q$

Simplify the arithmetic:

$2 q + 8 = (2 q - 1) - 2 q$

Group like terms:

$2 q + 8 = (2 q - 2 q) - 1$

Simplify the arithmetic:

$2 q + 8 = - 1$

Subtract from both sides:

$(2 q + 8) - 8 = - 1 - 8$

Simplify the arithmetic:

$2 q = - 1 - 8$

Simplify the arithmetic:

$2 q = - 9$

Divide both sides by :

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

Simplify the fraction:

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

10 additional steps

$(4 q + 8) = - (2 q - 1)$

Expand the parentheses:

$(4 q + 8) = - 2 q + 1$

Add to both sides:

$(4 q + 8) + 2 q = (- 2 q + 1) + 2 q$

Group like terms:

$(4 q + 2 q) + 8 = (- 2 q + 1) + 2 q$

Simplify the arithmetic:

$6 q + 8 = (- 2 q + 1) + 2 q$

Group like terms:

$6 q + 8 = (- 2 q + 2 q) + 1$

Simplify the arithmetic:

$6 q + 8 = 1$

Subtract from both sides:

$(6 q + 8) - 8 = 1 - 8$

Simplify the arithmetic:

$6 q = 1 - 8$

Simplify the arithmetic:

$6 q = - 7$

Divide both sides by :

$\frac{(6 q)}{6} = \frac{- 7}{6}$

Simplify the fraction:

$q = \frac{- 7}{6}$

3. List the solutions

$q = - \frac{9}{2}, - \frac{7}{6}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 4 q + 8 |$
$y = | 2 q - 1 |$
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 q

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 q

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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