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Solution - Absolute value equations

Exact form: x=107,2
x=\frac{10}{7} , 2
Mixed number form: x=137,2
x=1\frac{3}{7} , 2
Decimal form: x=1.429,2
x=1.429 , 2

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
|2x2|=|5x+8|
without the absolute value bars:

|x|=|y||2x2|=|5x+8|
x=+y(2x2)=(5x+8)
x=y(2x2)=(5x+8)
+x=y(2x2)=(5x+8)
x=y(2x2)=(5x+8)

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||2x2|=|5x+8|
x=+y , +x=y(2x2)=(5x+8)
x=y , x=y(2x2)=(5x+8)

2. Solve the two equations for x

9 additional steps

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

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

7x-2=(-5x+8)+5x

Group like terms:

7x-2=(-5x+5x)+8

Simplify the arithmetic:

7x2=8

Add to both sides:

(7x-2)+2=8+2

Simplify the arithmetic:

7x=8+2

Simplify the arithmetic:

7x=10

Divide both sides by :

(7x)7=107

Simplify the fraction:

x=107

14 additional steps

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

Expand the parentheses:

(2x-2)=5x-8

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

-3x-2=(5x-8)-5x

Group like terms:

-3x-2=(5x-5x)-8

Simplify the arithmetic:

3x2=8

Add to both sides:

(-3x-2)+2=-8+2

Simplify the arithmetic:

3x=8+2

Simplify the arithmetic:

3x=6

Divide both sides by :

(-3x)-3=-6-3

Cancel out the negatives:

3x3=-6-3

Simplify the fraction:

x=-6-3

Cancel out the negatives:

x=63

Find the greatest common factor of the numerator and denominator:

x=(2·3)(1·3)

Factor out and cancel the greatest common factor:

x=2

3. List the solutions

x=107,2
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|2x2|
y=|5x+8|
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.