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Solution - Absolute value equations

Exact form: x=9
x=-9

Other Ways to Solve

Absolute value equations

Step-by-step explanation

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

|x+6|+|x+12|=0

Add |x+12| to both sides of the equation:

|x+6|+|x+12||x+12|=|x+12|

Simplify the arithmetic

|x+6|=|x+12|

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+6|=|x+12|
without the absolute value bars:

|x|=|y||x+6|=|x+12|
x=+y(x+6)=(x+12)
x=y(x+6)=(x+12)
+x=y(x+6)=(x+12)
x=y(x+6)=(x+12)

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+6|=|x+12|
x=+y , +x=y(x+6)=(x+12)
x=y , x=y(x+6)=(x+12)

3. Solve the two equations for x

12 additional steps

(x+6)=-(x+12)

Expand the parentheses:

(x+6)=-x-12

Add to both sides:

(x+6)+x=(-x-12)+x

Group like terms:

(x+x)+6=(-x-12)+x

Simplify the arithmetic:

2x+6=(-x-12)+x

Group like terms:

2x+6=(-x+x)-12

Simplify the arithmetic:

2x+6=12

Subtract from both sides:

(2x+6)-6=-12-6

Simplify the arithmetic:

2x=126

Simplify the arithmetic:

2x=18

Divide both sides by :

(2x)2=-182

Simplify the fraction:

x=-182

Find the greatest common factor of the numerator and denominator:

x=(-9·2)(1·2)

Factor out and cancel the greatest common factor:

x=9

6 additional steps

(x+6)=-(-(x+12))

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(x+6)=x+12

Subtract from both sides:

(x+6)-x=(x+12)-x

Group like terms:

(x-x)+6=(x+12)-x

Simplify the arithmetic:

6=(x+12)-x

Group like terms:

6=(x-x)+12

Simplify the arithmetic:

6=12

The statement is false:

6=12

The equation is false so it has no solution.

4. List the solutions

x=9
(1 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|x+6|
y=|x+12|
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.