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Solution - Absolute value equations

Exact form: x=1,4
x=1 , 4

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

|x|=|y||x+2|=|3x+6|
x=+y(x+2)=(3x+6)
x=y(x+2)=(3x+6)
+x=y(x+2)=(3x+6)
x=y(x+2)=(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+2|=|3x+6|
x=+y , +x=y(x+2)=(3x+6)
x=y , x=y(x+2)=(3x+6)

2. Solve the two equations for x

10 additional steps

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

4x+2=(-3x+6)+3x

Group like terms:

4x+2=(-3x+3x)+6

Simplify the arithmetic:

4x+2=6

Subtract from both sides:

(4x+2)-2=6-2

Simplify the arithmetic:

4x=62

Simplify the arithmetic:

4x=4

Divide both sides by :

(4x)4=44

Simplify the fraction:

x=44

Simplify the fraction:

x=1

14 additional steps

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

Expand the parentheses:

(x+2)=3x-6

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x+2=6

Subtract from both sides:

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

Simplify the arithmetic:

2x=62

Simplify the arithmetic:

2x=8

Divide both sides by :

(-2x)-2=-8-2

Cancel out the negatives:

2x2=-8-2

Simplify the fraction:

x=-8-2

Cancel out the negatives:

x=82

Find the greatest common factor of the numerator and denominator:

x=(4·2)(1·2)

Factor out and cancel the greatest common factor:

x=4

3. List the solutions

x=1,4
(2 solution(s))

4. Graph

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