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Solution - Absolute value equations

Exact form: x=32,3
x=\frac{3}{2} , 3
Mixed number form: x=112,3
x=1\frac{1}{2} , 3
Decimal form: x=1.5,3
x=1.5 , 3

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

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

2. Solve the two equations for x

7 additional steps

x=(-3x+6)

Add to both sides:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

4x=6

Divide both sides by :

(4x)4=64

Simplify the fraction:

x=64

Find the greatest common factor of the numerator and denominator:

x=(3·2)(2·2)

Factor out and cancel the greatest common factor:

x=32

10 additional steps

x=-(-3x+6)

Expand the parentheses:

x=3x6

Subtract from both sides:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x=6

Divide both sides by :

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

Cancel out the negatives:

2x2=-6-2

Simplify the fraction:

x=-6-2

Cancel out the negatives:

x=62

Find the greatest common factor of the numerator and denominator:

x=(3·2)(1·2)

Factor out and cancel the greatest common factor:

x=3

3. List the solutions

x=32,3
(2 solution(s))

4. Graph

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