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Solution - Absolute value equations

Exact form: x=1
x=-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
|x2|=|x+4|
without the absolute value bars:

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

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

2. Solve the two equations for x

5 additional steps

(x-2)=(x+4)

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

-2=(x+4)-x

Group like terms:

-2=(x-x)+4

Simplify the arithmetic:

2=4

The statement is false:

2=4

The equation is false so it has no solution.

11 additional steps

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

Expand the parentheses:

(x-2)=-x-4

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x2=4

Add to both sides:

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

Simplify the arithmetic:

2x=4+2

Simplify the arithmetic:

2x=2

Divide both sides by :

(2x)2=-22

Simplify the fraction:

x=-22

Simplify the fraction:

x=1

3. Graph

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