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Solution - Absolute value equations

Exact form: x=12,2
x=\frac{1}{2} , 2
Decimal form: x=0.5,2
x=0.5 , 2

Other Ways to Solve

Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

|5x+4|3|x|=0

Add 3|x| to both sides of the equation:

|5x+4|3|x|+3|x|=3|x|

Simplify the arithmetic

|5x+4|=3|x|

2. 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
|5x+4|=3|x|
without the absolute value bars:

|x|=|y||5x+4|=3|x|
x=+y(5x+4)=3(x)
x=y(5x+4)=3((x))
+x=y(5x+4)=3(x)
x=y(5x+4)=3(x)

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||5x+4|=3|x|
x=+y , +x=y(5x+4)=3(x)
x=y , x=y(5x+4)=3((x))

3. Solve the two equations for x

12 additional steps

(-5x+4)=3x

Subtract from both sides:

(-5x+4)-3x=(3x)-3x

Group like terms:

(-5x-3x)+4=(3x)-3x

Simplify the arithmetic:

-8x+4=(3x)-3x

Simplify the arithmetic:

8x+4=0

Subtract from both sides:

(-8x+4)-4=0-4

Simplify the arithmetic:

8x=04

Simplify the arithmetic:

8x=4

Divide both sides by :

(-8x)-8=-4-8

Cancel out the negatives:

8x8=-4-8

Simplify the fraction:

x=-4-8

Cancel out the negatives:

x=48

Find the greatest common factor of the numerator and denominator:

x=(1·4)(2·4)

Factor out and cancel the greatest common factor:

x=12

14 additional steps

(-5x+4)=3·-x

Group like terms:

(-5x+4)=(3·-1)x

Multiply the coefficients:

(-5x+4)=-3x

Add to both sides:

(-5x+4)+3x=(-3x)+3x

Group like terms:

(-5x+3x)+4=(-3x)+3x

Simplify the arithmetic:

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

Simplify the arithmetic:

2x+4=0

Subtract from both sides:

(-2x+4)-4=0-4

Simplify the arithmetic:

2x=04

Simplify the arithmetic:

2x=4

Divide both sides by :

(-2x)-2=-4-2

Cancel out the negatives:

2x2=-4-2

Simplify the fraction:

x=-4-2

Cancel out the negatives:

x=42

Find the greatest common factor of the numerator and denominator:

x=(2·2)(1·2)

Factor out and cancel the greatest common factor:

x=2

4. List the solutions

x=12,2
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|5x+4|
y=3|x|
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.