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Solution - Absolute value equations

Exact form: y=13,1
y=-13 , -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
|2y+5|=12|3y-3|
without the absolute value bars:

|x|=|y||2y+5|=12|3y-3|
x=+y(2y+5)=12(3y-3)
x=-y(2y+5)=12(-(3y-3))
+x=y(2y+5)=12(3y-3)
-x=y-(2y+5)=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+5|=12|3y-3|
x=+y , +x=y(2y+5)=12(3y-3)
x=-y , -x=y(2y+5)=12(-(3y-3))

2. Solve the two equations for y

23 additional steps

(2y+5)=12·(3y-3)

Multiply the fraction(s):

(2y+5)=(1·(3y-3))2

Break up the fraction:

(2y+5)=3y2+-32

Subtract from both sides:

(2y+5)-3y2=(3y2+-32)-3y2

Group like terms:

(2y+-32y)+5=(3y2+-32)-3y2

Group the coefficients:

(2+-32)y+5=(3y2+-32)-3y2

Convert the integer into a fraction:

(42+-32)y+5=(3y2+-32)-3y2

Combine the fractions:

(4-3)2y+5=(3y2+-32)-3y2

Combine the numerators:

12y+5=(3y2+-32)-3y2

Group like terms:

12·y+5=(3y2+-32y)+-32

Combine the fractions:

12·y+5=(3-3)2y+-32

Combine the numerators:

12·y+5=02y+-32

Reduce the zero numerator:

12y+5=0y+-32

Simplify the arithmetic:

12y+5=-32

Subtract from both sides:

(12y+5)-5=(-32)-5

Simplify the arithmetic:

12y=(-32)-5

Convert the integer into a fraction:

12y=-32+-102

Combine the fractions:

12y=(-3-10)2

Combine the numerators:

12y=-132

Multiply both sides by inverse fraction :

(12y)·21=(-132)·21

Group like terms:

(12·2)y=(-132)·21

Multiply the coefficients:

(1·2)2y=(-132)·21

Simplify the fraction:

y=(-132)·21

Multiply the fraction(s):

y=(-13·2)2

Simplify the arithmetic:

y=13

24 additional steps

(2y+5)=12·(-(3y-3))

Multiply the fraction(s):

(2y+5)=(1·(-(3y-3)))2

Expand the parentheses:

(2y+5)=(-3y+3)2

Break up the fraction:

(2y+5)=-3y2+32

Add to both sides:

(2y+5)+32·y=(-3y2+32)+32y

Group like terms:

(2y+32·y)+5=(-3y2+32)+32y

Group the coefficients:

(2+32)y+5=(-3y2+32)+32y

Convert the integer into a fraction:

(42+32)y+5=(-3y2+32)+32y

Combine the fractions:

(4+3)2·y+5=(-3y2+32)+32y

Combine the numerators:

72·y+5=(-3y2+32)+32y

Group like terms:

72·y+5=(-3y2+32y)+32

Combine the fractions:

72·y+5=(-3+3)2y+32

Combine the numerators:

72·y+5=02y+32

Reduce the zero numerator:

72y+5=0y+32

Simplify the arithmetic:

72y+5=32

Subtract from both sides:

(72y+5)-5=(32)-5

Simplify the arithmetic:

72y=(32)-5

Convert the integer into a fraction:

72y=32+-102

Combine the fractions:

72y=(3-10)2

Combine the numerators:

72y=-72

Multiply both sides by inverse fraction :

(72y)·27=(-72)·27

Group like terms:

(72·27)y=(-72)·27

Multiply the coefficients:

(7·2)(2·7)y=(-72)·27

Simplify the fraction:

y=(-72)·27

Multiply the fraction(s):

y=(-7·2)(2·7)

Simplify the arithmetic:

y=1

3. List the solutions

y=13,1
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|2y+5|
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.