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Solution - Absolute value equations

Exact form:

b = 3, 5

b=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
$| 2 b - 9 | = | b - 6 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 2 b - 9 \| = \| b - 6 \|$
$x = + y$	$(2 b - 9) = (b - 6)$
$x = - y$	$(2 b - 9) = - (b - 6)$
$+ x = y$	$(2 b - 9) = (b - 6)$
$- x = y$	$- (2 b - 9) = (b - 6)$

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:

$\| x \| = \| y \|$	$\| 2 b - 9 \| = \| b - 6 \|$
$x = + y$ , $+ x = y$	$(2 b - 9) = (b - 6)$
$x = - y$ , $- x = y$	$(2 b - 9) = - (b - 6)$

2. Solve the two equations for b

7 additional steps

$(2 b - 9) = (b - 6)$

Subtract from both sides:

$(2 b - 9) - b = (b - 6) - b$

Group like terms:

$(2 b - b) - 9 = (b - 6) - b$

Simplify the arithmetic:

$b - 9 = (b - 6) - b$

Group like terms:

$b - 9 = (b - b) - 6$

Simplify the arithmetic:

$b - 9 = - 6$

Add to both sides:

$(b - 9) + 9 = - 6 + 9$

Simplify the arithmetic:

$b = - 6 + 9$

Simplify the arithmetic:

$b = 3$

12 additional steps

$(2 b - 9) = - (b - 6)$

Expand the parentheses:

$(2 b - 9) = - b + 6$

Add to both sides:

$(2 b - 9) + b = (- b + 6) + b$

Group like terms:

$(2 b + b) - 9 = (- b + 6) + b$

Simplify the arithmetic:

$3 b - 9 = (- b + 6) + b$

Group like terms:

$3 b - 9 = (- b + b) + 6$

Simplify the arithmetic:

$3 b - 9 = 6$

Add to both sides:

$(3 b - 9) + 9 = 6 + 9$

Simplify the arithmetic:

$3 b = 6 + 9$

Simplify the arithmetic:

$3 b = 15$

Divide both sides by :

$\frac{(3 b)}{3} = \frac{15}{3}$

Simplify the fraction:

$b = \frac{15}{3}$

Find the greatest common factor of the numerator and denominator:

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

Factor out and cancel the greatest common factor:

$b = 5$

3. List the solutions

$b = 3, 5$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 2 b - 9 |$
$y = | b - 6 |$
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 b

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 b

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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