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Solution - Absolute value equations

Exact form: x=-12,-14
x=-\frac{1}{2} , -\frac{1}{4}
Decimal form: x=0.5,0.25
x=-0.5 , -0.25

Other Ways to Solve

Absolute value equations

Step-by-step explanation

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

|5x+2|+|x+1|=0

Add |x+1| to both sides of the equation:

|5x+2|+|x+1||x+1|=|x+1|

Simplify the arithmetic

|5x+2|=|x+1|

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
|5x+2|=|x+1|
without the absolute value bars:

|x|=|y||5x+2|=|x+1|
x=+y(5x+2)=(x+1)
x=y(5x+2)=(x+1)
+x=y(5x+2)=(x+1)
x=y(5x+2)=(x+1)

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||5x+2|=|x+1|
x=+y , +x=y(5x+2)=(x+1)
x=y , x=y(5x+2)=(x+1)

3. Solve the two equations for x

12 additional steps

(5x+2)=-(x+1)

Expand the parentheses:

(5x+2)=-x-1

Add to both sides:

(5x+2)+x=(-x-1)+x

Group like terms:

(5x+x)+2=(-x-1)+x

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

6x+2=1

Subtract from both sides:

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

Simplify the arithmetic:

6x=12

Simplify the arithmetic:

6x=3

Divide both sides by :

(6x)6=-36

Simplify the fraction:

x=-36

Find the greatest common factor of the numerator and denominator:

x=(-1·3)(2·3)

Factor out and cancel the greatest common factor:

x=-12

10 additional steps

(5x+2)=-(-(x+1))

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(5x+2)=x+1

Subtract from both sides:

(5x+2)-x=(x+1)-x

Group like terms:

(5x-x)+2=(x+1)-x

Simplify the arithmetic:

4x+2=(x+1)-x

Group like terms:

4x+2=(x-x)+1

Simplify the arithmetic:

4x+2=1

Subtract from both sides:

(4x+2)-2=1-2

Simplify the arithmetic:

4x=12

Simplify the arithmetic:

4x=1

Divide both sides by :

(4x)4=-14

Simplify the fraction:

x=-14

4. List the solutions

x=-12,-14
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|5x+2|
y=|x+1|
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.