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Solution - Absolute value equations

Exact form: x=6,-25
x=6 , -\frac{2}{5}
Decimal form: x=6,0.4
x=6 , -0.4

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
|3x2|=2|x+2|
without the absolute value bars:

|x|=|y||3x2|=2|x+2|
x=+y(3x2)=2(x+2)
x=y(3x2)=2((x+2))
+x=y(3x2)=2(x+2)
x=y(3x2)=2(x+2)

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||3x2|=2|x+2|
x=+y , +x=y(3x2)=2(x+2)
x=y , x=y(3x2)=2((x+2))

2. Solve the two equations for x

9 additional steps

(3x-2)=2·(x+2)

Expand the parentheses:

(3x-2)=2x+2·2

Simplify the arithmetic:

(3x-2)=2x+4

Subtract from both sides:

(3x-2)-2x=(2x+4)-2x

Group like terms:

(3x-2x)-2=(2x+4)-2x

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

x2=4

Add to both sides:

(x-2)+2=4+2

Simplify the arithmetic:

x=4+2

Simplify the arithmetic:

x=6

14 additional steps

(3x-2)=2·(-(x+2))

Expand the parentheses:

(3x-2)=2·(-x-2)

(3x-2)=2·-x+2·-2

Group like terms:

(3x-2)=(2·-1)x+2·-2

Multiply the coefficients:

(3x-2)=-2x+2·-2

Simplify the arithmetic:

(3x-2)=-2x-4

Add to both sides:

(3x-2)+2x=(-2x-4)+2x

Group like terms:

(3x+2x)-2=(-2x-4)+2x

Simplify the arithmetic:

5x-2=(-2x-4)+2x

Group like terms:

5x-2=(-2x+2x)-4

Simplify the arithmetic:

5x2=4

Add to both sides:

(5x-2)+2=-4+2

Simplify the arithmetic:

5x=4+2

Simplify the arithmetic:

5x=2

Divide both sides by :

(5x)5=-25

Simplify the fraction:

x=-25

3. List the solutions

x=6,-25
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|3x2|
y=2|x+2|
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.