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Solution - Absolute value equations

Exact form: x=6,1
x=-6 , 1

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
|3x10|=|5x+2|
without the absolute value bars:

|x|=|y||3x10|=|5x+2|
x=+y(3x10)=(5x+2)
x=y(3x10)=(5x+2)
+x=y(3x10)=(5x+2)
x=y(3x10)=(5x+2)

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||3x10|=|5x+2|
x=+y , +x=y(3x10)=(5x+2)
x=y , x=y(3x10)=(5x+2)

2. Solve the two equations for x

13 additional steps

(3x-10)=(5x+2)

Subtract from both sides:

(3x-10)-5x=(5x+2)-5x

Group like terms:

(3x-5x)-10=(5x+2)-5x

Simplify the arithmetic:

-2x-10=(5x+2)-5x

Group like terms:

-2x-10=(5x-5x)+2

Simplify the arithmetic:

2x10=2

Add to both sides:

(-2x-10)+10=2+10

Simplify the arithmetic:

2x=2+10

Simplify the arithmetic:

2x=12

Divide both sides by :

(-2x)-2=12-2

Cancel out the negatives:

2x2=12-2

Simplify the fraction:

x=12-2

Move the negative sign from the denominator to the numerator:

x=-122

Find the greatest common factor of the numerator and denominator:

x=(-6·2)(1·2)

Factor out and cancel the greatest common factor:

x=6

11 additional steps

(3x-10)=-(5x+2)

Expand the parentheses:

(3x-10)=-5x-2

Add to both sides:

(3x-10)+5x=(-5x-2)+5x

Group like terms:

(3x+5x)-10=(-5x-2)+5x

Simplify the arithmetic:

8x-10=(-5x-2)+5x

Group like terms:

8x-10=(-5x+5x)-2

Simplify the arithmetic:

8x10=2

Add to both sides:

(8x-10)+10=-2+10

Simplify the arithmetic:

8x=2+10

Simplify the arithmetic:

8x=8

Divide both sides by :

(8x)8=88

Simplify the fraction:

x=88

Simplify the fraction:

x=1

3. List the solutions

x=6,1
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|3x10|
y=|5x+2|
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.