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Solution - Absolute value equations

Exact form: f=23
f=\frac{2}{3}
Decimal form: f=0.667
f=0.667

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
|f-43|=|f|
without the absolute value bars:

|x|=|y||f-43|=|f|
x=+y(f-43)=(f)
x=-y(f-43)=-(f)
+x=y(f-43)=(f)
-x=y-(f-43)=(f)

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||f-43|=|f|
x=+y , +x=y(f-43)=(f)
x=-y , -x=y(f-43)=-(f)

2. Solve the two equations for f

4 additional steps

(f+-43)=f

Subtract from both sides:

(f+-43)-f=f-f

Group like terms:

(f-f)+-43=f-f

Simplify the arithmetic:

-43=f-f

Simplify the arithmetic:

-43=0

The statement is false:

-43=0

The equation is false so it has no solution.

13 additional steps

(f+-43)=-f

Add to both sides:

(f+-43)+f=-f+f

Group like terms:

(f+f)+-43=-f+f

Simplify the arithmetic:

2f+-43=-f+f

Simplify the arithmetic:

2f+-43=0

Add to both sides:

(2f+-43)+43=0+43

Combine the fractions:

2f+(-4+4)3=0+43

Combine the numerators:

2f+03=0+43

Reduce the zero numerator:

2f+0=0+43

Simplify the arithmetic:

2f=0+43

Simplify the arithmetic:

2f=43

Divide both sides by :

(2f)2=(43)2

Simplify the fraction:

f=(43)2

Simplify the arithmetic:

f=4(3·2)

f=23

3. Graph

Each line represents the function of one side of the equation:
y=|f-43|
y=|f|
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.