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Solution - Absolute value equations

Exact form: x=-23,-45
x=-\frac{2}{3} , -\frac{4}{5}
Decimal form: x=0.667,0.8
x=-0.667 , -0.8

Other Ways to Solve

Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

|2x+1|+|7x+5|=0

Add |7x+5| to both sides of the equation:

|2x+1|+|7x+5||7x+5|=|7x+5|

Simplify the arithmetic

|2x+1|=|7x+5|

2. 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
|2x+1|=|7x+5|
without the absolute value bars:

|x|=|y||2x+1|=|7x+5|
x=+y(2x+1)=(7x+5)
x=y(2x+1)=(7x+5)
+x=y(2x+1)=(7x+5)
x=y(2x+1)=(7x+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||2x+1|=|7x+5|
x=+y , +x=y(2x+1)=(7x+5)
x=y , x=y(2x+1)=(7x+5)

3. Solve the two equations for x

12 additional steps

(2x+1)=-(7x+5)

Expand the parentheses:

(2x+1)=-7x-5

Add to both sides:

(2x+1)+7x=(-7x-5)+7x

Group like terms:

(2x+7x)+1=(-7x-5)+7x

Simplify the arithmetic:

9x+1=(-7x-5)+7x

Group like terms:

9x+1=(-7x+7x)-5

Simplify the arithmetic:

9x+1=5

Subtract from both sides:

(9x+1)-1=-5-1

Simplify the arithmetic:

9x=51

Simplify the arithmetic:

9x=6

Divide both sides by :

(9x)9=-69

Simplify the fraction:

x=-69

Find the greatest common factor of the numerator and denominator:

x=(-2·3)(3·3)

Factor out and cancel the greatest common factor:

x=-23

12 additional steps

(2x+1)=-(-(7x+5))

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(2x+1)=7x+5

Subtract from both sides:

(2x+1)-7x=(7x+5)-7x

Group like terms:

(2x-7x)+1=(7x+5)-7x

Simplify the arithmetic:

-5x+1=(7x+5)-7x

Group like terms:

-5x+1=(7x-7x)+5

Simplify the arithmetic:

5x+1=5

Subtract from both sides:

(-5x+1)-1=5-1

Simplify the arithmetic:

5x=51

Simplify the arithmetic:

5x=4

Divide both sides by :

(-5x)-5=4-5

Cancel out the negatives:

5x5=4-5

Simplify the fraction:

x=4-5

Move the negative sign from the denominator to the numerator:

x=-45

4. List the solutions

x=-23,-45
(2 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|2x+1|
y=|7x+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.