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Solution - Absolute value equations

Exact form: =12,20
=12 , 20

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
|4|=|x16|
without the absolute value bars:

|x|=|y||4|=|x16|
x=+y(4)=(x16)
x=y(4)=(x16)
+x=y(4)=(x16)
x=y(4)=(x16)

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||4|=|x16|
x=+y , +x=y(4)=(x16)
x=y , x=y(4)=(x16)

2. Solve the two equations for

3 additional steps

-4=(x-16)

Swap sides:

(x-16)=-4

Add to both sides:

(x-16)+16=-4+16

Simplify the arithmetic:

x=4+16

Simplify the arithmetic:

x=12

7 additional steps

-4=-(x-16)

Expand the parentheses:

4=x+16

Swap sides:

x+16=4

Subtract from both sides:

(-x+16)-16=-4-16

Simplify the arithmetic:

x=416

Simplify the arithmetic:

x=20

Multiply both sides by :

-x·-1=-20·-1

Remove the one(s):

x=-20·-1

Simplify the arithmetic:

x=20

3. List the solutions

=12,20
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|4|
y=|x16|
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.