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Solution - Absolute value equations

Exact form: x=-66,-545
x=-66 , -\frac{54}{5}
Mixed number form: x=-66,-1045
x=-66 , -10\frac{4}{5}
Decimal form: x=66,10.8
x=-66 , -10.8

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
13|x-3|=12|x+20|
without the absolute value bars:

|x|=|y|13|x-3|=12|x+20|
x=+y13(x-3)=12(x+20)
x=-y13(x-3)=12(-(x+20))
+x=y13(x-3)=12(x+20)
-x=y13(-(x-3))=12(x+20)

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|13|x-3|=12|x+20|
x=+y , +x=y13(x-3)=12(x+20)
x=-y , -x=y13(x-3)=12(-(x+20))

2. Solve the two equations for x

29 additional steps

13·(x-3)=12·(x+20)

Multiply the fraction(s):

(1·(x-3))3=12·(x+20)

Break up the fraction:

x3+-33=12·(x+20)

Find the greatest common factor of the numerator and denominator:

x3+(-1·3)(1·3)=12·(x+20)

Factor out and cancel the greatest common factor:

x3-1=12·(x+20)

Multiply the fraction(s):

x3-1=(1·(x+20))2

Break up the fraction:

x3-1=x2+202

Find the greatest common factor of the numerator and denominator:

x3-1=x2+(10·2)(1·2)

Factor out and cancel the greatest common factor:

x3-1=x2+10

Subtract from both sides:

(x3-1)-x2=(x2+10)-x2

Group like terms:

(x3+-12x)-1=(x2+10)-x2

Group the coefficients:

(13+-12)x-1=(x2+10)-x2

Find the lowest common denominator:

((1·2)(3·2)+(-1·3)(2·3))x-1=(x2+10)-x2

Multiply the denominators:

((1·2)6+(-1·3)6)x-1=(x2+10)-x2

Multiply the numerators:

(26+-36)x-1=(x2+10)-x2

Combine the fractions:

(2-3)6x-1=(x2+10)-x2

Combine the numerators:

-16x-1=(x2+10)-x2

Group like terms:

-16·x-1=(x2+-12x)+10

Combine the fractions:

-16·x-1=(1-1)2x+10

Combine the numerators:

-16·x-1=02x+10

Reduce the zero numerator:

-16x-1=0x+10

Simplify the arithmetic:

-16x-1=10

Add to both sides:

(-16x-1)+1=10+1

Simplify the arithmetic:

-16x=10+1

Simplify the arithmetic:

-16x=11

Multiply both sides by inverse fraction :

(-16x)·6-1=11·6-1

Group like terms:

(-16·-6)x=11·6-1

Multiply the coefficients:

(-1·-6)6x=11·6-1

Simplify the arithmetic:

1x=11·6-1

x=11·6-1

Simplify the arithmetic:

x=66

30 additional steps

13·(x-3)=12·(-(x+20))

Multiply the fraction(s):

(1·(x-3))3=12·(-(x+20))

Break up the fraction:

x3+-33=12·(-(x+20))

Find the greatest common factor of the numerator and denominator:

x3+(-1·3)(1·3)=12·(-(x+20))

Factor out and cancel the greatest common factor:

x3-1=12·(-(x+20))

Multiply the fraction(s):

x3-1=(1·(-(x+20)))2

Expand the parentheses:

x3-1=(-x-20)2

Break up the fraction:

x3-1=-x2+-202

Find the greatest common factor of the numerator and denominator:

x3-1=-x2+(-10·2)(1·2)

Factor out and cancel the greatest common factor:

x3-1=-x2-10

Add to both sides:

(x3-1)+12·x=(-x2-10)+12x

Group like terms:

(x3+12·x)-1=(-x2-10)+12x

Group the coefficients:

(13+12)x-1=(-x2-10)+12x

Find the lowest common denominator:

((1·2)(3·2)+(1·3)(2·3))x-1=(-x2-10)+12x

Multiply the denominators:

((1·2)6+(1·3)6)x-1=(-x2-10)+12x

Multiply the numerators:

(26+36)x-1=(-x2-10)+12x

Combine the fractions:

(2+3)6·x-1=(-x2-10)+12x

Combine the numerators:

56·x-1=(-x2-10)+12x

Group like terms:

56·x-1=(-x2+12x)-10

Combine the fractions:

56·x-1=(-1+1)2x-10

Combine the numerators:

56·x-1=02x-10

Reduce the zero numerator:

56x-1=0x-10

Simplify the arithmetic:

56x-1=-10

Add to both sides:

(56x-1)+1=-10+1

Simplify the arithmetic:

56x=-10+1

Simplify the arithmetic:

56x=-9

Multiply both sides by inverse fraction :

(56x)·65=-9·65

Group like terms:

(56·65)x=-9·65

Multiply the coefficients:

(5·6)(6·5)x=-9·65

Simplify the fraction:

x=-9·65

Multiply the fraction(s):

x=(-9·6)5

Simplify the arithmetic:

x=-545

3. List the solutions

x=-66,-545
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=13|x-3|
y=12|x+20|
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.