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Solution - Absolute value equations

Exact form: x=72,74
x=\frac{7}{2} , \frac{7}{4}
Mixed number form: x=312,134
x=3\frac{1}{2} , 1\frac{3}{4}
Decimal form: x=3.5,1.75
x=3.5 , 1.75

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
|12x|=|32x-72|
without the absolute value bars:

|x|=|y||12x|=|32x-72|
x=+y(12x)=(32x-72)
x=-y(12x)=-(32x-72)
+x=y(12x)=(32x-72)
-x=y-(12x)=(32x-72)

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||12x|=|32x-72|
x=+y , +x=y(12x)=(32x-72)
x=-y , -x=y(12x)=-(32x-72)

2. Solve the two equations for x

13 additional steps

12·x=(32x+-72)

Subtract from both sides:

(12x)-32·x=(32x+-72)-32x

Combine the fractions:

(1-3)2·x=(32·x+-72)-32x

Combine the numerators:

-22·x=(32·x+-72)-32x

Find the greatest common factor of the numerator and denominator:

(-1·2)(1·2)·x=(32·x+-72)-32x

Factor out and cancel the greatest common factor:

-1x=(32·x+-72)-32x

Simplify the arithmetic:

-x=(32·x+-72)-32x

Group like terms:

-x=(32·x+-32x)+-72

Combine the fractions:

-x=(3-3)2x+-72

Combine the numerators:

-x=02x+-72

Reduce the zero numerator:

-x=0x+-72

Simplify the arithmetic:

-x=-72

Multiply both sides by :

-x·-1=(-72)·-1

Remove the one(s):

x=(-72)·-1

Remove the one(s):

x=72

14 additional steps

12x=-(32x+-72)

Expand the parentheses:

12·x=-32x+72

Add to both sides:

(12x)+32·x=(-32x+72)+32x

Combine the fractions:

(1+3)2·x=(-32·x+72)+32x

Combine the numerators:

42·x=(-32·x+72)+32x

Find the greatest common factor of the numerator and denominator:

(2·2)(1·2)·x=(-32·x+72)+32x

Factor out and cancel the greatest common factor:

2x=(-32·x+72)+32x

Group like terms:

2x=(-32·x+32x)+72

Combine the fractions:

2x=(-3+3)2x+72

Combine the numerators:

2x=02x+72

Reduce the zero numerator:

2x=0x+72

Simplify the arithmetic:

2x=72

Divide both sides by :

(2x)2=(72)2

Simplify the fraction:

x=(72)2

Simplify the arithmetic:

x=7(2·2)

x=74

3. List the solutions

x=72,74
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|12x|
y=|32x-72|
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.