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Solution - Absolute value equations

Exact form: x=-38,-54
x=-\frac{3}{8} , -\frac{5}{4}
Mixed number form: x=-38,-114
x=-\frac{3}{8} , -1\frac{1}{4}
Decimal form: x=0.375,1.25
x=-0.375 , -1.25

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

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

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

2. Solve the two equations for x

17 additional steps

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

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

-4x+12=(3x+2)-3x

Group like terms:

-4x+12=(3x-3x)+2

Simplify the arithmetic:

-4x+12=2

Subtract from both sides:

(-4x+12)-12=2-12

Combine the fractions:

-4x+(1-1)2=2-12

Combine the numerators:

-4x+02=2-12

Reduce the zero numerator:

-4x+0=2-12

Simplify the arithmetic:

-4x=2-12

Convert the integer into a fraction:

-4x=42+-12

Combine the fractions:

-4x=(4-1)2

Combine the numerators:

-4x=32

Divide both sides by :

(-4x)-4=(32)-4

Cancel out the negatives:

4x4=(32)-4

Simplify the fraction:

x=(32)-4

Simplify the arithmetic:

x=3(2·-4)

x=-38

17 additional steps

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

Expand the parentheses:

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x+12=-2

Subtract from both sides:

(2x+12)-12=-2-12

Combine the fractions:

2x+(1-1)2=-2-12

Combine the numerators:

2x+02=-2-12

Reduce the zero numerator:

2x+0=-2-12

Simplify the arithmetic:

2x=-2-12

Convert the integer into a fraction:

2x=-42+-12

Combine the fractions:

2x=(-4-1)2

Combine the numerators:

2x=-52

Divide both sides by :

(2x)2=(-52)2

Simplify the fraction:

x=(-52)2

Simplify the arithmetic:

x=-5(2·2)

x=-54

3. List the solutions

x=-38,-54
(2 solution(s))

4. Graph

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