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Solution - Absolute value equations

Exact form: y=12,12
y=12 , -12

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
|y12|=|y+12|
without the absolute value bars:

|x|=|y||y12|=|y+12|
x=+y(y12)=(y+12)
x=y(y12)=(y+12)
+x=y(y12)=(y+12)
x=y(y12)=(y+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||y12|=|y+12|
x=+y , +x=y(y12)=(y+12)
x=y , x=y(y12)=(y+12)

2. Solve the two equations for y

11 additional steps

(y-12)=(-y+12)

Add to both sides:

(y-12)+y=(-y+12)+y

Group like terms:

(y+y)-12=(-y+12)+y

Simplify the arithmetic:

2y-12=(-y+12)+y

Group like terms:

2y-12=(-y+y)+12

Simplify the arithmetic:

2y12=12

Add to both sides:

(2y-12)+12=12+12

Simplify the arithmetic:

2y=12+12

Simplify the arithmetic:

2y=24

Divide both sides by :

(2y)2=242

Simplify the fraction:

y=242

Find the greatest common factor of the numerator and denominator:

y=(12·2)(1·2)

Factor out and cancel the greatest common factor:

y=12

5 additional steps

(y-12)=-(-y+12)

Expand the parentheses:

(y-12)=y-12

Subtract from both sides:

(y-12)-y=(y-12)-y

Group like terms:

(y-y)-12=(y-12)-y

Simplify the arithmetic:

-12=(y-12)-y

Group like terms:

-12=(y-y)-12

Simplify the arithmetic:

12=12

3. List the solutions

y=12,12
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|y12|
y=|y+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.