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Solution - Absolute value equations

Exact form: x=-12,-110
x=-\frac{1}{2} , -\frac{1}{10}
Decimal form: x=0.5,0.1
x=-0.5 , -0.1

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|=|3x+12|
without the absolute value bars:

|x|=|y||2x|=|3x+12|
x=+y(2x)=(3x+12)
x=-y(2x)=-(3x+12)
+x=y(2x)=(3x+12)
-x=y-(2x)=(3x+12)

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|=|3x+12|
x=+y , +x=y(2x)=(3x+12)
x=-y , -x=y(2x)=-(3x+12)

2. Solve the two equations for x

6 additional steps

2x=(3x+12)

Subtract from both sides:

(2x)-3x=(3x+12)-3x

Simplify the arithmetic:

-x=(3x+12)-3x

Group like terms:

-x=(3x-3x)+12

Simplify the arithmetic:

-x=12

Multiply both sides by :

-x·-1=(12)·-1

Remove the one(s):

x=(12)·-1

Remove the one(s):

x=-12

8 additional steps

2x=-(3x+12)

Expand the parentheses:

2x=-3x+-12

Add to both sides:

(2x)+3x=(-3x+-12)+3x

Simplify the arithmetic:

5x=(-3x+-12)+3x

Group like terms:

5x=(-3x+3x)+-12

Simplify the arithmetic:

5x=-12

Divide both sides by :

(5x)5=(-12)5

Simplify the fraction:

x=(-12)5

Simplify the arithmetic:

x=-1(2·5)

x=-110

3. List the solutions

x=-12,-110
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|2x|
y=|3x+12|
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.