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Solution - Absolute value equations

Exact form: y=-3,37
y=-3 , \frac{3}{7}
Decimal form: y=3,0.429
y=-3 , 0.429

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
|2y|=12|3y-3|
without the absolute value bars:

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

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

2. Solve the two equations for y

17 additional steps

2y=12·(3y-3)

Multiply the fraction(s):

2y=(1·(3y-3))2

Break up the fraction:

2y=3y2+-32

Subtract from both sides:

(2y)-3y2=(3y2+-32)-3y2

Group the coefficients:

(2+-32)y=(3y2+-32)-3y2

Convert the integer into a fraction:

(42+-32)y=(3y2+-32)-3y2

Combine the fractions:

(4-3)2y=(3y2+-32)-3y2

Combine the numerators:

12y=(3y2+-32)-3y2

Group like terms:

12·y=(3y2+-32y)+-32

Combine the fractions:

12·y=(3-3)2y+-32

Combine the numerators:

12·y=02y+-32

Reduce the zero numerator:

12y=0y+-32

Simplify the arithmetic:

12y=-32

Multiply both sides by inverse fraction :

(12y)·21=(-32)·21

Group like terms:

(12·2)y=(-32)·21

Multiply the coefficients:

(1·2)2y=(-32)·21

Simplify the fraction:

y=(-32)·21

Multiply the fraction(s):

y=(-3·2)2

Simplify the arithmetic:

y=3

18 additional steps

2y=12·(-(3y-3))

Multiply the fraction(s):

2y=(1·(-(3y-3)))2

Expand the parentheses:

2y=(-3y+3)2

Break up the fraction:

2y=-3y2+32

Add to both sides:

(2y)+32·y=(-3y2+32)+32y

Group the coefficients:

(2+32)y=(-3y2+32)+32y

Convert the integer into a fraction:

(42+32)y=(-3y2+32)+32y

Combine the fractions:

(4+3)2·y=(-3y2+32)+32y

Combine the numerators:

72·y=(-3y2+32)+32y

Group like terms:

72·y=(-3y2+32y)+32

Combine the fractions:

72·y=(-3+3)2y+32

Combine the numerators:

72·y=02y+32

Reduce the zero numerator:

72y=0y+32

Simplify the arithmetic:

72y=32

Multiply both sides by inverse fraction :

(72y)·27=(32)·27

Group like terms:

(72·27)y=(32)·27

Multiply the coefficients:

(7·2)(2·7)y=(32)·27

Simplify the fraction:

y=(32)·27

Multiply the fraction(s):

y=(3·2)(2·7)

Simplify the arithmetic:

y=37

3. List the solutions

y=-3,37
(2 solution(s))

4. Graph

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