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Solution - Absolute value equations

Exact form: x=73,13
x=\frac{7}{3} , 13
Mixed number form: x=213,13
x=2\frac{1}{3} , 13
Decimal form: x=2.333,13
x=2.333 , 13

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+3|=2|x+5|
without the absolute value bars:

|x|=|y||x+3|=2|x+5|
x=+y(x+3)=2(x+5)
x=y(x+3)=2((x+5))
+x=y(x+3)=2(x+5)
x=y(x+3)=2(x+5)

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+3|=2|x+5|
x=+y , +x=y(x+3)=2(x+5)
x=y , x=y(x+3)=2((x+5))

2. Solve the two equations for x

13 additional steps

(x+3)=2·(-x+5)

Expand the parentheses:

(x+3)=2·-x+2·5

Group like terms:

(x+3)=(2·-1)x+2·5

Multiply the coefficients:

(x+3)=-2x+2·5

Simplify the arithmetic:

(x+3)=-2x+10

Add to both sides:

(x+3)+2x=(-2x+10)+2x

Group like terms:

(x+2x)+3=(-2x+10)+2x

Simplify the arithmetic:

3x+3=(-2x+10)+2x

Group like terms:

3x+3=(-2x+2x)+10

Simplify the arithmetic:

3x+3=10

Subtract from both sides:

(3x+3)-3=10-3

Simplify the arithmetic:

3x=103

Simplify the arithmetic:

3x=7

Divide both sides by :

(3x)3=73

Simplify the fraction:

x=73

13 additional steps

(x+3)=2·(-(-x+5))

Expand the parentheses:

(x+3)=2·(x-5)

(x+3)=2x+2·-5

Simplify the arithmetic:

(x+3)=2x-10

Subtract from both sides:

(x+3)-2x=(2x-10)-2x

Group like terms:

(x-2x)+3=(2x-10)-2x

Simplify the arithmetic:

-x+3=(2x-10)-2x

Group like terms:

-x+3=(2x-2x)-10

Simplify the arithmetic:

x+3=10

Subtract from both sides:

(-x+3)-3=-10-3

Simplify the arithmetic:

x=103

Simplify the arithmetic:

x=13

Multiply both sides by :

-x·-1=-13·-1

Remove the one(s):

x=-13·-1

Simplify the arithmetic:

x=13

3. List the solutions

x=73,13
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|x+3|
y=2|x+5|
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.