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Solution - Absolute value equations

Exact form: r=116
r=\frac{1}{16}
Decimal form: r=0.062
r=0.062

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
|r+34|=|r-78|
without the absolute value bars:

|x|=|y||r+34|=|r-78|
x=+y(r+34)=(r-78)
x=-y(r+34)=-(r-78)
+x=y(r+34)=(r-78)
-x=y-(r+34)=(r-78)

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||r+34|=|r-78|
x=+y , +x=y(r+34)=(r-78)
x=-y , -x=y(r+34)=-(r-78)

2. Solve the two equations for r

5 additional steps

(r+34)=(r+-78)

Subtract from both sides:

(r+34)-r=(r+-78)-r

Group like terms:

(r-r)+34=(r+-78)-r

Simplify the arithmetic:

34=(r+-78)-r

Group like terms:

34=(r-r)+-78

Simplify the arithmetic:

34=-78

The statement is false:

34=-78

The equation is false so it has no solution.

19 additional steps

(r+34)=-(r+-78)

Expand the parentheses:

(r+34)=-r+78

Add to both sides:

(r+34)+r=(-r+78)+r

Group like terms:

(r+r)+34=(-r+78)+r

Simplify the arithmetic:

2r+34=(-r+78)+r

Group like terms:

2r+34=(-r+r)+78

Simplify the arithmetic:

2r+34=78

Subtract from both sides:

(2r+34)-34=(78)-34

Combine the fractions:

2r+(3-3)4=(78)-34

Combine the numerators:

2r+04=(78)-34

Reduce the zero numerator:

2r+0=(78)-34

Simplify the arithmetic:

2r=(78)-34

Find the lowest common denominator:

2r=78+(-3·2)(4·2)

Multiply the denominators:

2r=78+(-3·2)8

Multiply the numerators:

2r=78+-68

Combine the fractions:

2r=(7-6)8

Combine the numerators:

2r=18

Divide both sides by :

(2r)2=(18)2

Simplify the fraction:

r=(18)2

Simplify the arithmetic:

r=1(8·2)

r=116

3. Graph

Each line represents the function of one side of the equation:
y=|r+34|
y=|r-78|
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.