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Solution - Absolute value equations

Exact form: c=-59
c=-\frac{5}{9}
Decimal form: c=0.556
c=-0.556

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
|9c7|=|9c3|
without the absolute value bars:

|x|=|y||9c7|=|9c3|
x=+y(9c7)=(9c3)
x=y(9c7)=(9c3)
+x=y(9c7)=(9c3)
x=y(9c7)=(9c3)

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||9c7|=|9c3|
x=+y , +x=y(9c7)=(9c3)
x=y , x=y(9c7)=(9c3)

2. Solve the two equations for c

5 additional steps

(-9c-7)=(-9c-3)

Add to both sides:

(-9c-7)+9c=(-9c-3)+9c

Group like terms:

(-9c+9c)-7=(-9c-3)+9c

Simplify the arithmetic:

-7=(-9c-3)+9c

Group like terms:

-7=(-9c+9c)-3

Simplify the arithmetic:

7=3

The statement is false:

7=3

The equation is false so it has no solution.

14 additional steps

(-9c-7)=-(-9c-3)

Expand the parentheses:

(-9c-7)=9c+3

Subtract from both sides:

(-9c-7)-9c=(9c+3)-9c

Group like terms:

(-9c-9c)-7=(9c+3)-9c

Simplify the arithmetic:

-18c-7=(9c+3)-9c

Group like terms:

-18c-7=(9c-9c)+3

Simplify the arithmetic:

18c7=3

Add to both sides:

(-18c-7)+7=3+7

Simplify the arithmetic:

18c=3+7

Simplify the arithmetic:

18c=10

Divide both sides by :

(-18c)-18=10-18

Cancel out the negatives:

18c18=10-18

Simplify the fraction:

c=10-18

Move the negative sign from the denominator to the numerator:

c=-1018

Find the greatest common factor of the numerator and denominator:

c=(-5·2)(9·2)

Factor out and cancel the greatest common factor:

c=-59

3. Graph

Each line represents the function of one side of the equation:
y=|9c7|
y=|9c3|
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.