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Solution - Absolute value equations

Exact form:

p = 23, - 1

p=23 , -1

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
$| 9 p - 3 | = | 8 p + 20 |$
without the absolute value bars:

$\| x \| = \| y \|$	$\| 9 p - 3 \| = \| 8 p + 20 \|$
$x = + y$	$(9 p - 3) = (8 p + 20)$
$x = - y$	$(9 p - 3) = - (8 p + 20)$
$+ x = y$	$(9 p - 3) = (8 p + 20)$
$- x = y$	$- (9 p - 3) = (8 p + 20)$

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:

$\| x \| = \| y \|$	$\| 9 p - 3 \| = \| 8 p + 20 \|$
$x = + y$ , $+ x = y$	$(9 p - 3) = (8 p + 20)$
$x = - y$ , $- x = y$	$(9 p - 3) = - (8 p + 20)$

2. Solve the two equations for p

7 additional steps

$(9 p - 3) = (8 p + 20)$

Subtract from both sides:

$(9 p - 3) - 8 p = (8 p + 20) - 8 p$

Group like terms:

$(9 p - 8 p) - 3 = (8 p + 20) - 8 p$

Simplify the arithmetic:

$p - 3 = (8 p + 20) - 8 p$

Group like terms:

$p - 3 = (8 p - 8 p) + 20$

Simplify the arithmetic:

$p - 3 = 20$

Add to both sides:

$(p - 3) + 3 = 20 + 3$

Simplify the arithmetic:

$p = 20 + 3$

Simplify the arithmetic:

$p = 23$

11 additional steps

$(9 p - 3) = - (8 p + 20)$

Expand the parentheses:

$(9 p - 3) = - 8 p - 20$

Add to both sides:

$(9 p - 3) + 8 p = (- 8 p - 20) + 8 p$

Group like terms:

$(9 p + 8 p) - 3 = (- 8 p - 20) + 8 p$

Simplify the arithmetic:

$17 p - 3 = (- 8 p - 20) + 8 p$

Group like terms:

$17 p - 3 = (- 8 p + 8 p) - 20$

Simplify the arithmetic:

$17 p - 3 = - 20$

Add to both sides:

$(17 p - 3) + 3 = - 20 + 3$

Simplify the arithmetic:

$17 p = - 20 + 3$

Simplify the arithmetic:

$17 p = - 17$

Divide both sides by :

$\frac{(17 p)}{17} = \frac{- 17}{17}$

Simplify the fraction:

$p = \frac{- 17}{17}$

Simplify the fraction:

$p = - 1$

3. List the solutions

$p = 23, - 1$
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
$y = | 9 p - 3 |$
$y = | 8 p + 20 |$
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 p

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 p

3. List the solutions

4. Graph

Why learn this

Terms and topics

Related links

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