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Solution - Absolute value equations

Exact form: x=4,-14
x=4 , -\frac{1}{4}
Decimal form: x=4,0.25
x=4 , -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
|5x3|=|3x+5|
without the absolute value bars:

|x|=|y||5x3|=|3x+5|
x=+y(5x3)=(3x+5)
x=y(5x3)=(3x+5)
+x=y(5x3)=(3x+5)
x=y(5x3)=(3x+5)

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||5x3|=|3x+5|
x=+y , +x=y(5x3)=(3x+5)
x=y , x=y(5x3)=(3x+5)

2. Solve the two equations for x

11 additional steps

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

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

2x3=5

Add to both sides:

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

Simplify the arithmetic:

2x=5+3

Simplify the arithmetic:

2x=8

Divide both sides by :

(2x)2=82

Simplify the fraction:

x=82

Find the greatest common factor of the numerator and denominator:

x=(4·2)(1·2)

Factor out and cancel the greatest common factor:

x=4

12 additional steps

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

Expand the parentheses:

(5x-3)=-3x-5

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

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

Group like terms:

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

Simplify the arithmetic:

8x3=5

Add to both sides:

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

Simplify the arithmetic:

8x=5+3

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=4,-14
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|5x3|
y=|3x+5|
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.