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Solution - Absolute value equations

Exact form: x=2,2
x=2 , -2

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+4|=|2x2|
without the absolute value bars:

|x|=|y||x+4|=|2x2|
x=+y(x+4)=(2x2)
x=y(x+4)=(2x2)
+x=y(x+4)=(2x2)
x=y(x+4)=(2x2)

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+4|=|2x2|
x=+y , +x=y(x+4)=(2x2)
x=y , x=y(x+4)=(2x2)

2. Solve the two equations for x

13 additional steps

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

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

3x+4=2

Subtract from both sides:

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

Simplify the arithmetic:

3x=24

Simplify the arithmetic:

3x=6

Divide both sides by :

(-3x)-3=-6-3

Cancel out the negatives:

3x3=-6-3

Simplify the fraction:

x=-6-3

Cancel out the negatives:

x=63

Find the greatest common factor of the numerator and denominator:

x=(2·3)(1·3)

Factor out and cancel the greatest common factor:

x=2

8 additional steps

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

Expand the parentheses:

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

x+4=2

Subtract from both sides:

(x+4)-4=2-4

Simplify the arithmetic:

x=24

Simplify the arithmetic:

x=2

3. List the solutions

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

4. Graph

Each line represents the function of one side of the equation:
y=|x+4|
y=|2x2|
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.