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Solution - Absolute value equations

Exact form:

c = 7, - 3

c=7 , -3

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
$| 3 c + 4 | = | 2 c + 11 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 3 c + 4 \| = \| 2 c + 11 \|$
$x = + y$	$(3 c + 4) = (2 c + 11)$
$x = - y$	$(3 c + 4) = - (2 c + 11)$
$+ x = y$	$(3 c + 4) = (2 c + 11)$
$- x = y$	$- (3 c + 4) = (2 c + 11)$

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:

$\| x \| = \| y \|$	$\| 3 c + 4 \| = \| 2 c + 11 \|$
$x = + y$ , $+ x = y$	$(3 c + 4) = (2 c + 11)$
$x = - y$ , $- x = y$	$(3 c + 4) = - (2 c + 11)$

2. Solve the two equations for c

7 additional steps

$(3 c + 4) = (2 c + 11)$

Subtract from both sides:

$(3 c + 4) - 2 c = (2 c + 11) - 2 c$

Group like terms:

$(3 c - 2 c) + 4 = (2 c + 11) - 2 c$

Simplify the arithmetic:

$c + 4 = (2 c + 11) - 2 c$

Group like terms:

$c + 4 = (2 c - 2 c) + 11$

Simplify the arithmetic:

$c + 4 = 11$

Subtract from both sides:

$(c + 4) - 4 = 11 - 4$

Simplify the arithmetic:

$c = 11 - 4$

Simplify the arithmetic:

$c = 7$

12 additional steps

$(3 c + 4) = - (2 c + 11)$

Expand the parentheses:

$(3 c + 4) = - 2 c - 11$

Add to both sides:

$(3 c + 4) + 2 c = (- 2 c - 11) + 2 c$

Group like terms:

$(3 c + 2 c) + 4 = (- 2 c - 11) + 2 c$

Simplify the arithmetic:

$5 c + 4 = (- 2 c - 11) + 2 c$

Group like terms:

$5 c + 4 = (- 2 c + 2 c) - 11$

Simplify the arithmetic:

$5 c + 4 = - 11$

Subtract from both sides:

$(5 c + 4) - 4 = - 11 - 4$

Simplify the arithmetic:

$5 c = - 11 - 4$

Simplify the arithmetic:

$5 c = - 15$

Divide both sides by :

$\frac{(5 c)}{5} = \frac{- 15}{5}$

Simplify the fraction:

$c = \frac{- 15}{5}$

Find the greatest common factor of the numerator and denominator:

$c = \frac{(- 3 \cdot 5)}{(1 \cdot 5)}$

Factor out and cancel the greatest common factor:

$c = - 3$

3. List the solutions

$c = 7, - 3$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 3 c + 4 |$
$y = | 2 c + 11 |$
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. List the solutions

4. 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. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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