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Solution - Absolute value equations

Exact form: x=12,-2
x=\frac{1}{2} , -2
Decimal form: x=0.5,2
x=0.5 , -2

Other Ways to Solve

Absolute value equations

Step-by-step explanation

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

|3x+1|+|x3|=0

Add |x3| to both sides of the equation:

|3x+1|+|x3||x3|=|x3|

Simplify the arithmetic

|3x+1|=|x3|

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
|3x+1|=|x3|
without the absolute value bars:

|x|=|y||3x+1|=|x3|
x=+y(3x+1)=(x3)
x=y(3x+1)=(x3)
+x=y(3x+1)=(x3)
x=y(3x+1)=(x3)

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||3x+1|=|x3|
x=+y , +x=y(3x+1)=(x3)
x=y , x=y(3x+1)=(x3)

3. Solve the two equations for x

12 additional steps

(3x+1)=-(x-3)

Expand the parentheses:

(3x+1)=-x+3

Add to both sides:

(3x+1)+x=(-x+3)+x

Group like terms:

(3x+x)+1=(-x+3)+x

Simplify the arithmetic:

4x+1=(-x+3)+x

Group like terms:

4x+1=(-x+x)+3

Simplify the arithmetic:

4x+1=3

Subtract from both sides:

(4x+1)-1=3-1

Simplify the arithmetic:

4x=31

Simplify the arithmetic:

4x=2

Divide both sides by :

(4x)4=24

Simplify the fraction:

x=24

Find the greatest common factor of the numerator and denominator:

x=(1·2)(2·2)

Factor out and cancel the greatest common factor:

x=12

12 additional steps

(3x+1)=-(-(x-3))

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(3x+1)=x-3

Subtract from both sides:

(3x+1)-x=(x-3)-x

Group like terms:

(3x-x)+1=(x-3)-x

Simplify the arithmetic:

2x+1=(x-3)-x

Group like terms:

2x+1=(x-x)-3

Simplify the arithmetic:

2x+1=3

Subtract from both sides:

(2x+1)-1=-3-1

Simplify the arithmetic:

2x=31

Simplify the arithmetic:

2x=4

Divide both sides by :

(2x)2=-42

Simplify the fraction:

x=-42

Find the greatest common factor of the numerator and denominator:

x=(-2·2)(1·2)

Factor out and cancel the greatest common factor:

x=2

4. List the solutions

x=12,-2
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|3x+1|
y=|x3|
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.