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Solution - Absolute value equations

Exact form: x=6,0
x=6 , 0

Other Ways to Solve

Absolute value equations

Step-by-step explanation

1. 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
|3x6|=|x+6|
without the absolute value bars:

|x|=|y||3x6|=|x+6|
x=+y(3x6)=(x+6)
x=y(3x6)=(x+6)
+x=y(3x6)=(x+6)
x=y(3x6)=(x+6)

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||3x6|=|x+6|
x=+y , +x=y(3x6)=(x+6)
x=y , x=y(3x6)=(x+6)

2. Solve the two equations for x

11 additional steps

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

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x6=6

Add to both sides:

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

Simplify the arithmetic:

2x=6+6

Simplify the arithmetic:

2x=12

Divide both sides by :

(2x)2=122

Simplify the fraction:

x=122

Find the greatest common factor of the numerator and denominator:

x=(6·2)(1·2)

Factor out and cancel the greatest common factor:

x=6

9 additional steps

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

Expand the parentheses:

(3x-6)=-x-6

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

4x6=6

Add to both sides:

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

Simplify the arithmetic:

4x=6+6

Simplify the arithmetic:

4x=0

Divide both sides by the coefficient:

x=0

3. List the solutions

x=6,0
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|3x6|
y=|x+6|
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.