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Solution - Absolute value equations

Exact form: x=-7,12
x=-7 , \frac{1}{2}
Decimal form: x=7,0.5
x=-7 , 0.5

Other Ways to Solve

Absolute value equations

Step-by-step explanation

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

|x8|3|x+2|=0

Add 3|x+2| to both sides of the equation:

|x8|3|x+2|+3|x+2|=3|x+2|

Simplify the arithmetic

|x8|=3|x+2|

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
|x8|=3|x+2|
without the absolute value bars:

|x|=|y||x8|=3|x+2|
x=+y(x8)=3(x+2)
x=y(x8)=3((x+2))
+x=y(x8)=3(x+2)
x=y(x8)=3(x+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||x8|=3|x+2|
x=+y , +x=y(x8)=3(x+2)
x=y , x=y(x8)=3((x+2))

3. Solve the two equations for x

15 additional steps

(x-8)=3·(x+2)

Expand the parentheses:

(x-8)=3x+3·2

Simplify the arithmetic:

(x-8)=3x+6

Subtract from both sides:

(x-8)-3x=(3x+6)-3x

Group like terms:

(x-3x)-8=(3x+6)-3x

Simplify the arithmetic:

-2x-8=(3x+6)-3x

Group like terms:

-2x-8=(3x-3x)+6

Simplify the arithmetic:

2x8=6

Add to both sides:

(-2x-8)+8=6+8

Simplify the arithmetic:

2x=6+8

Simplify the arithmetic:

2x=14

Divide both sides by :

(-2x)-2=14-2

Cancel out the negatives:

2x2=14-2

Simplify the fraction:

x=14-2

Move the negative sign from the denominator to the numerator:

x=-142

Find the greatest common factor of the numerator and denominator:

x=(-7·2)(1·2)

Factor out and cancel the greatest common factor:

x=7

16 additional steps

(x-8)=3·(-(x+2))

Expand the parentheses:

(x-8)=3·(-x-2)

(x-8)=3·-x+3·-2

Group like terms:

(x-8)=(3·-1)x+3·-2

Multiply the coefficients:

(x-8)=-3x+3·-2

Simplify the arithmetic:

(x-8)=-3x-6

Add to both sides:

(x-8)+3x=(-3x-6)+3x

Group like terms:

(x+3x)-8=(-3x-6)+3x

Simplify the arithmetic:

4x-8=(-3x-6)+3x

Group like terms:

4x-8=(-3x+3x)-6

Simplify the arithmetic:

4x8=6

Add to both sides:

(4x-8)+8=-6+8

Simplify the arithmetic:

4x=6+8

Simplify the arithmetic:

4x=2

Divide both sides by :

(4x)4=24

Simplify the fraction:

x=24

Find the greatest common factor of the numerator and denominator:

x=(1·2)(2·2)

Factor out and cancel the greatest common factor:

x=12

4. List the solutions

x=-7,12
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|x8|
y=3|x+2|
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.