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Solution - Absolute value equations

Exact form:

y = \frac{1}{9}, - 1

y=\frac{1}{9} , -1

Decimal form:

y = 0.111, - 1

y=0.111 , -1

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
$| 9 y - 1 | = | - 9 y + 1 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 9 y - 1 \| = \| - 9 y + 1 \|$
$x = + y$	$(9 y - 1) = (- 9 y + 1)$
$x = - y$	$(9 y - 1) = - (- 9 y + 1)$
$+ x = y$	$(9 y - 1) = (- 9 y + 1)$
$- x = y$	$- (9 y - 1) = (- 9 y + 1)$

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:

$\| x \| = \| y \|$	$\| 9 y - 1 \| = \| - 9 y + 1 \|$
$x = + y$ , $+ x = y$	$(9 y - 1) = (- 9 y + 1)$
$x = - y$ , $- x = y$	$(9 y - 1) = - (- 9 y + 1)$

2. Solve the two equations for y

11 additional steps

$(9 y - 1) = (- 9 y + 1)$

Add to both sides:

$(9 y - 1) + 9 y = (- 9 y + 1) + 9 y$

Group like terms:

$(9 y + 9 y) - 1 = (- 9 y + 1) + 9 y$

Simplify the arithmetic:

$18 y - 1 = (- 9 y + 1) + 9 y$

Group like terms:

$18 y - 1 = (- 9 y + 9 y) + 1$

Simplify the arithmetic:

$18 y - 1 = 1$

Add to both sides:

$(18 y - 1) + 1 = 1 + 1$

Simplify the arithmetic:

$18 y = 1 + 1$

Simplify the arithmetic:

$18 y = 2$

Divide both sides by :

$\frac{(18 y)}{18} = \frac{2}{18}$

Simplify the fraction:

$y = \frac{2}{18}$

Find the greatest common factor of the numerator and denominator:

$y = \frac{(1 \cdot 2)}{(9 \cdot 2)}$

Factor out and cancel the greatest common factor:

$y = \frac{1}{9}$

5 additional steps

$(9 y - 1) = - (- 9 y + 1)$

Expand the parentheses:

$(9 y - 1) = 9 y - 1$

Subtract from both sides:

$(9 y - 1) - 9 y = (9 y - 1) - 9 y$

Group like terms:

$(9 y - 9 y) - 1 = (9 y - 1) - 9 y$

Simplify the arithmetic:

$- 1 = (9 y - 1) - 9 y$

Group like terms:

$- 1 = (9 y - 9 y) - 1$

Simplify the arithmetic:

$- 1 = - 1$

3. List the solutions

$y = \frac{1}{9}, - 1$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 9 y - 1 |$
$y = | - 9 y + 1 |$
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 y

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 y

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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