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Solution - Absolute value equations

Exact form: x=23,-2
x=\frac{2}{3} , -2
Decimal form: x=0.667,2
x=0.667 , -2

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

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

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

2. Solve the two equations for x

10 additional steps

(-x+2)=2x

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Simplify the arithmetic:

3x+2=0

Subtract from both sides:

(-3x+2)-2=0-2

Simplify the arithmetic:

3x=02

Simplify the arithmetic:

3x=2

Divide both sides by :

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

Cancel out the negatives:

3x3=-2-3

Simplify the fraction:

x=-2-3

Cancel out the negatives:

x=23

5 additional steps

(-x+2)=-2x

Subtract from both sides:

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

Simplify the arithmetic:

-x=(-2x)-2

Add to both sides:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

x=2

3. List the solutions

x=23,-2
(2 solution(s))

4. Graph

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