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Solution - Absolute value equations

Exact form: x=8,85
x=8 , \frac{8}{5}
Mixed number form: x=8,135
x=8 , 1\frac{3}{5}
Decimal form: x=8,1.6
x=8 , 1.6

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|=|34x-2|
without the absolute value bars:

|x|=|y||12x|=|34x-2|
x=+y(12x)=(34x-2)
x=-y(12x)=-(34x-2)
+x=y(12x)=(34x-2)
-x=y-(12x)=(34x-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||12x|=|34x-2|
x=+y , +x=y(12x)=(34x-2)
x=-y , -x=y(12x)=-(34x-2)

2. Solve the two equations for x

17 additional steps

12·x=(34x-2)

Subtract from both sides:

(12x)-34·x=(34x-2)-34x

Group the coefficients:

(12+-34)x=(34·x-2)-34x

Find the lowest common denominator:

((1·2)(2·2)+-34)x=(34·x-2)-34x

Multiply the denominators:

((1·2)4+-34)x=(34·x-2)-34x

Multiply the numerators:

(24+-34)x=(34·x-2)-34x

Combine the fractions:

(2-3)4·x=(34·x-2)-34x

Combine the numerators:

-14·x=(34·x-2)-34x

Group like terms:

-14·x=(34·x+-34x)-2

Combine the fractions:

-14·x=(3-3)4x-2

Combine the numerators:

-14·x=04x-2

Reduce the zero numerator:

-14x=0x-2

Simplify the arithmetic:

-14x=-2

Multiply both sides by inverse fraction :

(-14x)·4-1=-2·4-1

Group like terms:

(-14·-4)x=-2·4-1

Multiply the coefficients:

(-1·-4)4x=-2·4-1

Simplify the arithmetic:

1x=-2·4-1

x=-2·4-1

Simplify the arithmetic:

x=8

18 additional steps

12x=-(34x-2)

Expand the parentheses:

12·x=-34x+2

Add to both sides:

(12x)+34·x=(-34x+2)+34x

Group the coefficients:

(12+34)x=(-34·x+2)+34x

Find the lowest common denominator:

((1·2)(2·2)+34)x=(-34·x+2)+34x

Multiply the denominators:

((1·2)4+34)x=(-34·x+2)+34x

Multiply the numerators:

(24+34)x=(-34·x+2)+34x

Combine the fractions:

(2+3)4·x=(-34·x+2)+34x

Combine the numerators:

54·x=(-34·x+2)+34x

Group like terms:

54·x=(-34·x+34x)+2

Combine the fractions:

54·x=(-3+3)4x+2

Combine the numerators:

54·x=04x+2

Reduce the zero numerator:

54x=0x+2

Simplify the arithmetic:

54x=2

Multiply both sides by inverse fraction :

(54x)·45=2·45

Group like terms:

(54·45)x=2·45

Multiply the coefficients:

(5·4)(4·5)x=2·45

Simplify the fraction:

x=2·45

Multiply the fraction(s):

x=(2·4)5

Simplify the arithmetic:

x=85

3. List the solutions

x=8,85
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|12x|
y=|34x-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.