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Solution - Absolute value equations

Exact form:

x = \frac{20}{7}, \frac{14}{11}

x=\frac{20}{7} , \frac{14}{11}

Mixed number form:

x = 2 \frac{6}{7}, 1 \frac{3}{11}

x=2\frac{6}{7} , 1\frac{3}{11}

Decimal form:

x = 2.857, 1.273

x=2.857 , 1.273

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
$| 9 x - 17 | = | 2 x + 3 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 9 x - 17 \| = \| 2 x + 3 \|$
$x = + y$	$(9 x - 17) = (2 x + 3)$
$x = - y$	$(9 x - 17) = - (2 x + 3)$
$+ x = y$	$(9 x - 17) = (2 x + 3)$
$- x = y$	$- (9 x - 17) = (2 x + 3)$

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:

$\| x \| = \| y \|$	$\| 9 x - 17 \| = \| 2 x + 3 \|$
$x = + y$ , $+ x = y$	$(9 x - 17) = (2 x + 3)$
$x = - y$ , $- x = y$	$(9 x - 17) = - (2 x + 3)$

2. Solve the two equations for x

9 additional steps

$(9 x - 17) = (2 x + 3)$

Subtract from both sides:

$(9 x - 17) - 2 x = (2 x + 3) - 2 x$

Group like terms:

$(9 x - 2 x) - 17 = (2 x + 3) - 2 x$

Simplify the arithmetic:

$7 x - 17 = (2 x + 3) - 2 x$

Group like terms:

$7 x - 17 = (2 x - 2 x) + 3$

Simplify the arithmetic:

$7 x - 17 = 3$

Add to both sides:

$(7 x - 17) + 17 = 3 + 17$

Simplify the arithmetic:

$7 x = 3 + 17$

Simplify the arithmetic:

$7 x = 20$

Divide both sides by :

$\frac{(7 x)}{7} = \frac{20}{7}$

Simplify the fraction:

$x = \frac{20}{7}$

10 additional steps

$(9 x - 17) = - (2 x + 3)$

Expand the parentheses:

$(9 x - 17) = - 2 x - 3$

Add to both sides:

$(9 x - 17) + 2 x = (- 2 x - 3) + 2 x$

Group like terms:

$(9 x + 2 x) - 17 = (- 2 x - 3) + 2 x$

Simplify the arithmetic:

$11 x - 17 = (- 2 x - 3) + 2 x$

Group like terms:

$11 x - 17 = (- 2 x + 2 x) - 3$

Simplify the arithmetic:

$11 x - 17 = - 3$

Add to both sides:

$(11 x - 17) + 17 = - 3 + 17$

Simplify the arithmetic:

$11 x = - 3 + 17$

Simplify the arithmetic:

$11 x = 14$

Divide both sides by :

$\frac{(11 x)}{11} = \frac{14}{11}$

Simplify the fraction:

$x = \frac{14}{11}$

3. List the solutions

$x = \frac{20}{7}, \frac{14}{11}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 9 x - 17 |$
$y = | 2 x + 3 |$
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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