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Solution - Absolute value equations

Exact form: x=-6,12
x=-6 , \frac{1}{2}
Decimal form: x=6,0.5
x=-6 , 0.5

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
|x7|=|3x+5|
without the absolute value bars:

|x|=|y||x7|=|3x+5|
x=+y(x7)=(3x+5)
x=y(x7)=(3x+5)
+x=y(x7)=(3x+5)
x=y(x7)=(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||x7|=|3x+5|
x=+y , +x=y(x7)=(3x+5)
x=y , x=y(x7)=(3x+5)

2. Solve the two equations for x

13 additional steps

(x-7)=(3x+5)

Subtract from both sides:

(x-7)-3x=(3x+5)-3x

Group like terms:

(x-3x)-7=(3x+5)-3x

Simplify the arithmetic:

-2x-7=(3x+5)-3x

Group like terms:

-2x-7=(3x-3x)+5

Simplify the arithmetic:

2x7=5

Add to both sides:

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

Simplify the arithmetic:

2x=5+7

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

12 additional steps

(x-7)=-(3x+5)

Expand the parentheses:

(x-7)=-3x-5

Add to both sides:

(x-7)+3x=(-3x-5)+3x

Group like terms:

(x+3x)-7=(-3x-5)+3x

Simplify the arithmetic:

4x-7=(-3x-5)+3x

Group like terms:

4x-7=(-3x+3x)-5

Simplify the arithmetic:

4x7=5

Add to both sides:

(4x-7)+7=-5+7

Simplify the arithmetic:

4x=5+7

Simplify the arithmetic:

4x=2

Divide both sides by :

(4x)4=24

Simplify the fraction:

x=24

Find the greatest common factor of the numerator and denominator:

x=(1·2)(2·2)

Factor out and cancel the greatest common factor:

x=12

3. List the solutions

x=-6,12
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|x7|
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.