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Solution - Absolute value equations

Exact form: x=-2,43
x=-2 , \frac{4}{3}
Mixed number form: x=-2,113
x=-2 , 1\frac{1}{3}
Decimal form: x=2,1.333
x=-2 , 1.333

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
|2x+1|=|x+3|
without the absolute value bars:

|x|=|y||2x+1|=|x+3|
x=+y(2x+1)=(x+3)
x=y(2x+1)=(x+3)
+x=y(2x+1)=(x+3)
x=y(2x+1)=(x+3)

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||2x+1|=|x+3|
x=+y , +x=y(2x+1)=(x+3)
x=y , x=y(2x+1)=(x+3)

2. Solve the two equations for x

10 additional steps

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

x+1=3

Subtract from both sides:

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

Simplify the arithmetic:

x=31

Simplify the arithmetic:

x=2

Multiply both sides by :

-x·-1=2·-1

Remove the one(s):

x=2·-1

Simplify the arithmetic:

x=2

12 additional steps

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

Expand the parentheses:

(-2x+1)=x-3

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

3x+1=3

Subtract from both sides:

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

Simplify the arithmetic:

3x=31

Simplify the arithmetic:

3x=4

Divide both sides by :

(-3x)-3=-4-3

Cancel out the negatives:

3x3=-4-3

Simplify the fraction:

x=-4-3

Cancel out the negatives:

x=43

3. List the solutions

x=-2,43
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|2x+1|
y=|x+3|
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.