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Solution - Absolute value equations

Exact form: =310,710
=\frac{3}{10} , \frac{7}{10}
Decimal form: =0.3,0.7
=0.3 , 0.7

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
|+15|=|-x+12|
without the absolute value bars:

|x|=|y||+15|=|-x+12|
x=+y(+15)=(-x+12)
x=-y(+15)=-(-x+12)
+x=y(+15)=(-x+12)
-x=y-(+15)=(-x+12)

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||+15|=|-x+12|
x=+y , +x=y(+15)=(-x+12)
x=-y , -x=y(+15)=-(-x+12)

2. Solve the two equations for

13 additional steps

(15)=(-x+12)

Swap sides:

(-x+12)=(15)

Subtract from both sides:

(-x+12)-12=(15)-12

Combine the fractions:

-x+(1-1)2=(15)-12

Combine the numerators:

-x+02=(15)-12

Reduce the zero numerator:

-x+0=(15)-12

Simplify the arithmetic:

-x=(15)-12

Find the lowest common denominator:

-x=(1·2)(5·2)+(-1·5)(2·5)

Multiply the denominators:

-x=(1·2)10+(-1·5)10

Multiply the numerators:

-x=210+-510

Combine the fractions:

-x=(2-5)10

Combine the numerators:

-x=-310

Multiply both sides by :

-x·-1=(-310)·-1

Remove the one(s):

x=(-310)·-1

Remove the one(s):

x=310

11 additional steps

(15)=-(-x+12)

Expand the parentheses:

(15)=x+-12

Swap sides:

x+-12=(15)

Add to both sides:

(x+-12)+12=(15)+12

Combine the fractions:

x+(-1+1)2=(15)+12

Combine the numerators:

x+02=(15)+12

Reduce the zero numerator:

x+0=(15)+12

Simplify the arithmetic:

x=(15)+12

Find the lowest common denominator:

x=(1·2)(5·2)+(1·5)(2·5)

Multiply the denominators:

x=(1·2)10+(1·5)10

Multiply the numerators:

x=210+510

Combine the fractions:

x=(2+5)10

Combine the numerators:

x=710

3. List the solutions

=310,710
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|+15|
y=|-x+12|
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.