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Solution - Absolute value equations

Exact form: x=4,4
x=-4 , -4

Other Ways to Solve

Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

|x+4|+|2x+8|=0

Add |2x+8| to both sides of the equation:

|x+4|+|2x+8||2x+8|=|2x+8|

Simplify the arithmetic

|x+4|=|2x+8|

2. Rewrite the equation without absolute value bars

Use the rules:
|x|=|y|x=±y and |x|=|y|±x=y
to write all four options of the equation
|x+4|=|2x+8|
without the absolute value bars:

|x|=|y||x+4|=|2x+8|
x=+y(x+4)=(2x+8)
x=y(x+4)=(2x+8)
+x=y(x+4)=(2x+8)
x=y(x+4)=(2x+8)

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||x+4|=|2x+8|
x=+y , +x=y(x+4)=(2x+8)
x=y , x=y(x+4)=(2x+8)

3. Solve the two equations for x

12 additional steps

(x+4)=-(2x+8)

Expand the parentheses:

(x+4)=-2x-8

Add to both sides:

(x+4)+2x=(-2x-8)+2x

Group like terms:

(x+2x)+4=(-2x-8)+2x

Simplify the arithmetic:

3x+4=(-2x-8)+2x

Group like terms:

3x+4=(-2x+2x)-8

Simplify the arithmetic:

3x+4=8

Subtract from both sides:

(3x+4)-4=-8-4

Simplify the arithmetic:

3x=84

Simplify the arithmetic:

3x=12

Divide both sides by :

(3x)3=-123

Simplify the fraction:

x=-123

Find the greatest common factor of the numerator and denominator:

x=(-4·3)(1·3)

Factor out and cancel the greatest common factor:

x=4

11 additional steps

(x+4)=-(-(2x+8))

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(x+4)=2x+8

Subtract from both sides:

(x+4)-2x=(2x+8)-2x

Group like terms:

(x-2x)+4=(2x+8)-2x

Simplify the arithmetic:

-x+4=(2x+8)-2x

Group like terms:

-x+4=(2x-2x)+8

Simplify the arithmetic:

x+4=8

Subtract from both sides:

(-x+4)-4=8-4

Simplify the arithmetic:

x=84

Simplify the arithmetic:

x=4

Multiply both sides by :

-x·-1=4·-1

Remove the one(s):

x=4·-1

Simplify the arithmetic:

x=4

4. List the solutions

x=4,4
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|x+4|
y=|2x+8|
The equation is true where the two lines cross.

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.