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Solution - Absolute value equations

Exact form: x=3,0
x=3 , 0

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
|5x+12|=|3x12|
without the absolute value bars:

|x|=|y||5x+12|=|3x12|
x=+y(5x+12)=(3x12)
x=y(5x+12)=(3x12)
+x=y(5x+12)=(3x12)
x=y(5x+12)=(3x12)

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+12|=|3x12|
x=+y , +x=y(5x+12)=(3x12)
x=y , x=y(5x+12)=(3x12)

2. Solve the two equations for x

13 additional steps

(-5x+12)=(3x-12)

Subtract from both sides:

(-5x+12)-3x=(3x-12)-3x

Group like terms:

(-5x-3x)+12=(3x-12)-3x

Simplify the arithmetic:

-8x+12=(3x-12)-3x

Group like terms:

-8x+12=(3x-3x)-12

Simplify the arithmetic:

8x+12=12

Subtract from both sides:

(-8x+12)-12=-12-12

Simplify the arithmetic:

8x=1212

Simplify the arithmetic:

8x=24

Divide both sides by :

(-8x)-8=-24-8

Cancel out the negatives:

8x8=-24-8

Simplify the fraction:

x=-24-8

Cancel out the negatives:

x=248

Find the greatest common factor of the numerator and denominator:

x=(3·8)(1·8)

Factor out and cancel the greatest common factor:

x=3

9 additional steps

(-5x+12)=-(3x-12)

Expand the parentheses:

(-5x+12)=-3x+12

Add to both sides:

(-5x+12)+3x=(-3x+12)+3x

Group like terms:

(-5x+3x)+12=(-3x+12)+3x

Simplify the arithmetic:

-2x+12=(-3x+12)+3x

Group like terms:

-2x+12=(-3x+3x)+12

Simplify the arithmetic:

2x+12=12

Subtract from both sides:

(-2x+12)-12=12-12

Simplify the arithmetic:

2x=1212

Simplify the arithmetic:

2x=0

Divide both sides by the coefficient:

x=0

3. List the solutions

x=3,0
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|5x+12|
y=|3x12|
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.