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Solution - Absolute value equations

Exact form:

c = \frac{7}{2}

c=\frac{7}{2}

Mixed number form:

c = 3 \frac{1}{2}

c=3\frac{1}{2}

Decimal form:

c = 3.5

c=3.5

See steps

Step-by-step explanation

1. Rewrite the equation without absolute value bars

Use the rules:
$| x | = | y |$ → $x = \pm y$ and $| x | = | y |$ → $\pm x = y$
to write all four options of the equation
$| c - 7 | = | c |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| c - 7 \| = \| c \|$
$x = + y$	$(c - 7) = (c)$
$x = - y$	$(c - 7) = - (c)$
$+ x = y$	$(c - 7) = (c)$
$- x = y$	$- (c - 7) = (c)$

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:

$\| x \| = \| y \|$	$\| c - 7 \| = \| c \|$
$x = + y$ , $+ x = y$	$(c - 7) = (c)$
$x = - y$ , $- x = y$	$(c - 7) = - (c)$

2. Solve the two equations for c

4 additional steps

$(c - 7) = c$

Subtract from both sides:

$(c - 7) - c = c - c$

Group like terms:

$(c - c) - 7 = c - c$

Simplify the arithmetic:

$- 7 = c - c$

Simplify the arithmetic:

$- 7 = 0$

The statement is false:

$- 7 = 0$

The equation is false so it has no solution.

8 additional steps

$(c - 7) = - c$

Add to both sides:

$(c - 7) + c = - c + c$

Group like terms:

$(c + c) - 7 = - c + c$

Simplify the arithmetic:

$2 c - 7 = - c + c$

Simplify the arithmetic:

$2 c - 7 = 0$

Add to both sides:

$(2 c - 7) + 7 = 0 + 7$

Simplify the arithmetic:

$2 c = 0 + 7$

Simplify the arithmetic:

$2 c = 7$

Divide both sides by :

$\frac{(2 c)}{2} = \frac{7}{2}$

Simplify the fraction:

$c = \frac{7}{2}$

3. Graph

Each line represents the function of one side of the equation:
$y = | c - 7 |$
$y = | c |$
The equation is true where the two lines cross.

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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.

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation without absolute value bars

2. Solve the two equations for c

3. Graph

Why learn this

Terms and topics

Related links

Solution - Absolute value equations

Step-by-step explanation

1. Rewrite the equation without absolute value bars

2. Solve the two equations for c

3. Graph

Why learn this

Terms and topics

Related links

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