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Solution - Absolute value equations

Exact form:

y = - 1

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

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

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:

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

2. Solve the two equations for y

5 additional steps

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

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

$4 = (y - 2) - y$

Group like terms:

$4 = (y - y) - 2$

Simplify the arithmetic:

$4 = - 2$

The statement is false:

$4 = - 2$

The equation is false so it has no solution.

11 additional steps

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

Expand the parentheses:

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

$2 y + 4 = 2$

Subtract from both sides:

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

Simplify the arithmetic:

$2 y = 2 - 4$

Simplify the arithmetic:

$2 y = - 2$

Divide both sides by :

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

Simplify the fraction:

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

Simplify the fraction:

$y = - 1$

3. Graph

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

Why learn this

Terms and topics

Related links

Latest Related Drills Solved