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Solution - Absolute value equations

Exact form: x=-3,-14
x=-3 , -\frac{1}{4}
Decimal form: x=3,0.25
x=-3 , -0.25

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
|3x2|=|5x+4|
without the absolute value bars:

|x|=|y||3x2|=|5x+4|
x=+y(3x2)=(5x+4)
x=y(3x2)=(5x+4)
+x=y(3x2)=(5x+4)
x=y(3x2)=(5x+4)

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||3x2|=|5x+4|
x=+y , +x=y(3x2)=(5x+4)
x=y , x=y(3x2)=(5x+4)

2. Solve the two equations for x

13 additional steps

(3x-2)=(5x+4)

Subtract from both sides:

(3x-2)-5x=(5x+4)-5x

Group like terms:

(3x-5x)-2=(5x+4)-5x

Simplify the arithmetic:

-2x-2=(5x+4)-5x

Group like terms:

-2x-2=(5x-5x)+4

Simplify the arithmetic:

2x2=4

Add to both sides:

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

Simplify the arithmetic:

2x=4+2

Simplify the arithmetic:

2x=6

Divide both sides by :

(-2x)-2=6-2

Cancel out the negatives:

2x2=6-2

Simplify the fraction:

x=6-2

Move the negative sign from the denominator to the numerator:

x=-62

Find the greatest common factor of the numerator and denominator:

x=(-3·2)(1·2)

Factor out and cancel the greatest common factor:

x=3

12 additional steps

(3x-2)=-(5x+4)

Expand the parentheses:

(3x-2)=-5x-4

Add to both sides:

(3x-2)+5x=(-5x-4)+5x

Group like terms:

(3x+5x)-2=(-5x-4)+5x

Simplify the arithmetic:

8x-2=(-5x-4)+5x

Group like terms:

8x-2=(-5x+5x)-4

Simplify the arithmetic:

8x2=4

Add to both sides:

(8x-2)+2=-4+2

Simplify the arithmetic:

8x=4+2

Simplify the arithmetic:

8x=2

Divide both sides by :

(8x)8=-28

Simplify the fraction:

x=-28

Find the greatest common factor of the numerator and denominator:

x=(-1·2)(4·2)

Factor out and cancel the greatest common factor:

x=-14

3. List the solutions

x=-3,-14
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|3x2|
y=|5x+4|
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.