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Solution - Absolute value equations

Exact form: x=-73,-5
x=-\frac{7}{3} , -5
Mixed number form: x=-213,-5
x=-2\frac{1}{3} , -5
Decimal form: x=2.333,5
x=-2.333 , -5

Other Ways to Solve

Absolute value equations

Step-by-step explanation

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

|x+1|+2|x+3|=0

Add 2|x+3| to both sides of the equation:

|x+1|+2|x+3|2|x+3|=2|x+3|

Simplify the arithmetic

|x+1|=2|x+3|

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

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

3. Solve the two equations for x

11 additional steps

(x+1)=-2·(x+3)

Expand the parentheses:

(x+1)=-2x-2·3

Simplify the arithmetic:

(x+1)=-2x-6

Add to both sides:

(x+1)+2x=(-2x-6)+2x

Group like terms:

(x+2x)+1=(-2x-6)+2x

Simplify the arithmetic:

3x+1=(-2x-6)+2x

Group like terms:

3x+1=(-2x+2x)-6

Simplify the arithmetic:

3x+1=6

Subtract from both sides:

(3x+1)-1=-6-1

Simplify the arithmetic:

3x=61

Simplify the arithmetic:

3x=7

Divide both sides by :

(3x)3=-73

Simplify the fraction:

x=-73

15 additional steps

(x+1)=-2·(-(x+3))

Expand the parentheses:

(x+1)=-2·(-x-3)

(x+1)=-2·-x-2·-3

Group like terms:

(x+1)=(-2·-1)x-2·-3

Multiply the coefficients:

(x+1)=2x-2·-3

Simplify the arithmetic:

(x+1)=2x+6

Subtract from both sides:

(x+1)-2x=(2x+6)-2x

Group like terms:

(x-2x)+1=(2x+6)-2x

Simplify the arithmetic:

-x+1=(2x+6)-2x

Group like terms:

-x+1=(2x-2x)+6

Simplify the arithmetic:

x+1=6

Subtract from both sides:

(-x+1)-1=6-1

Simplify the arithmetic:

x=61

Simplify the arithmetic:

x=5

Multiply both sides by :

-x·-1=5·-1

Remove the one(s):

x=5·-1

Simplify the arithmetic:

x=5

4. List the solutions

x=-73,-5
(2 solution(s))

5. Graph

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