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Solution - Absolute value equations

Exact form:

y = - 7, - \frac{3}{7}

y=-7 , -\frac{3}{7}

Decimal form:

y = - 7, - 0.429

y=-7 , -0.429

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
$| 4 y + 5 | = | 3 y - 2 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 4 y + 5 \| = \| 3 y - 2 \|$
$x = + y$	$(4 y + 5) = (3 y - 2)$
$x = - y$	$(4 y + 5) = - (3 y - 2)$
$+ x = y$	$(4 y + 5) = (3 y - 2)$
$- x = y$	$- (4 y + 5) = (3 y - 2)$

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:

$\| x \| = \| y \|$	$\| 4 y + 5 \| = \| 3 y - 2 \|$
$x = + y$ , $+ x = y$	$(4 y + 5) = (3 y - 2)$
$x = - y$ , $- x = y$	$(4 y + 5) = - (3 y - 2)$

2. Solve the two equations for y

7 additional steps

$(4 y + 5) = (3 y - 2)$

Subtract from both sides:

$(4 y + 5) - 3 y = (3 y - 2) - 3 y$

Group like terms:

$(4 y - 3 y) + 5 = (3 y - 2) - 3 y$

Simplify the arithmetic:

$y + 5 = (3 y - 2) - 3 y$

Group like terms:

$y + 5 = (3 y - 3 y) - 2$

Simplify the arithmetic:

$y + 5 = - 2$

Subtract from both sides:

$(y + 5) - 5 = - 2 - 5$

Simplify the arithmetic:

$y = - 2 - 5$

Simplify the arithmetic:

$y = - 7$

10 additional steps

$(4 y + 5) = - (3 y - 2)$

Expand the parentheses:

$(4 y + 5) = - 3 y + 2$

Add to both sides:

$(4 y + 5) + 3 y = (- 3 y + 2) + 3 y$

Group like terms:

$(4 y + 3 y) + 5 = (- 3 y + 2) + 3 y$

Simplify the arithmetic:

$7 y + 5 = (- 3 y + 2) + 3 y$

Group like terms:

$7 y + 5 = (- 3 y + 3 y) + 2$

Simplify the arithmetic:

$7 y + 5 = 2$

Subtract from both sides:

$(7 y + 5) - 5 = 2 - 5$

Simplify the arithmetic:

$7 y = 2 - 5$

Simplify the arithmetic:

$7 y = - 3$

Divide both sides by :

$\frac{(7 y)}{7} = \frac{- 3}{7}$

Simplify the fraction:

$y = \frac{- 3}{7}$

3. List the solutions

$y = - 7, - \frac{3}{7}$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 4 y + 5 |$
$y = | 3 y - 2 |$
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 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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