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Solution - Absolute value equations

Exact form: x=1315,745
x=\frac{13}{15} , \frac{7}{45}
Decimal form: x=0.867,0.156
x=0.867 , 0.156

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
|x+15|=|2x-23|
without the absolute value bars:

|x|=|y||x+15|=|2x-23|
x=+y(x+15)=(2x-23)
x=-y(x+15)=-(2x-23)
+x=y(x+15)=(2x-23)
-x=y-(x+15)=(2x-23)

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||x+15|=|2x-23|
x=+y , +x=y(x+15)=(2x-23)
x=-y , -x=y(x+15)=-(2x-23)

2. Solve the two equations for x

17 additional steps

(x+15)=(2x+-23)

Subtract from both sides:

(x+15)-2x=(2x+-23)-2x

Group like terms:

(x-2x)+15=(2x+-23)-2x

Simplify the arithmetic:

-x+15=(2x+-23)-2x

Group like terms:

-x+15=(2x-2x)+-23

Simplify the arithmetic:

-x+15=-23

Subtract from both sides:

(-x+15)-15=(-23)-15

Combine the fractions:

-x+(1-1)5=(-23)-15

Combine the numerators:

-x+05=(-23)-15

Reduce the zero numerator:

-x+0=(-23)-15

Simplify the arithmetic:

-x=(-23)-15

Find the lowest common denominator:

-x=(-2·5)(3·5)+(-1·3)(5·3)

Multiply the denominators:

-x=(-2·5)15+(-1·3)15

Multiply the numerators:

-x=-1015+-315

Combine the fractions:

-x=(-10-3)15

Combine the numerators:

-x=-1315

Multiply both sides by :

-x·-1=(-1315)·-1

Remove the one(s):

x=(-1315)·-1

Remove the one(s):

x=1315

19 additional steps

(x+15)=-(2x+-23)

Expand the parentheses:

(x+15)=-2x+23

Add to both sides:

(x+15)+2x=(-2x+23)+2x

Group like terms:

(x+2x)+15=(-2x+23)+2x

Simplify the arithmetic:

3x+15=(-2x+23)+2x

Group like terms:

3x+15=(-2x+2x)+23

Simplify the arithmetic:

3x+15=23

Subtract from both sides:

(3x+15)-15=(23)-15

Combine the fractions:

3x+(1-1)5=(23)-15

Combine the numerators:

3x+05=(23)-15

Reduce the zero numerator:

3x+0=(23)-15

Simplify the arithmetic:

3x=(23)-15

Find the lowest common denominator:

3x=(2·5)(3·5)+(-1·3)(5·3)

Multiply the denominators:

3x=(2·5)15+(-1·3)15

Multiply the numerators:

3x=1015+-315

Combine the fractions:

3x=(10-3)15

Combine the numerators:

3x=715

Divide both sides by :

(3x)3=(715)3

Simplify the fraction:

x=(715)3

Simplify the arithmetic:

x=7(15·3)

x=745

3. List the solutions

x=1315,745
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|x+15|
y=|2x-23|
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.