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Solution - Absolute value equations

Exact form: n=-113,3
n=-\frac{11}{3} , 3
Mixed number form: n=-323,3
n=-3\frac{2}{3} , 3
Decimal form: n=3.667,3
n=-3.667 , 3

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
2|n+7|=|4n+8|
without the absolute value bars:

|x|=|y|2|n+7|=|4n+8|
x=+y2(n+7)=(4n+8)
x=y2(n+7)=(4n+8)
+x=y2(n+7)=(4n+8)
x=y2((n+7))=(4n+8)

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|n+7|=|4n+8|
x=+y , +x=y2(n+7)=(4n+8)
x=y , x=y2(n+7)=(4n+8)

2. Solve the two equations for n

15 additional steps

-2·(n+7)=(4n+8)

Expand the parentheses:

-2n-2·7=(4n+8)

Simplify the arithmetic:

-2n-14=(4n+8)

Subtract from both sides:

(-2n-14)-4n=(4n+8)-4n

Group like terms:

(-2n-4n)-14=(4n+8)-4n

Simplify the arithmetic:

-6n-14=(4n+8)-4n

Group like terms:

-6n-14=(4n-4n)+8

Simplify the arithmetic:

6n14=8

Add to both sides:

(-6n-14)+14=8+14

Simplify the arithmetic:

6n=8+14

Simplify the arithmetic:

6n=22

Divide both sides by :

(-6n)-6=22-6

Cancel out the negatives:

6n6=22-6

Simplify the fraction:

n=22-6

Move the negative sign from the denominator to the numerator:

n=-226

Find the greatest common factor of the numerator and denominator:

n=(-11·2)(3·2)

Factor out and cancel the greatest common factor:

n=-113

14 additional steps

-2·(n+7)=-(4n+8)

Expand the parentheses:

-2n-2·7=-(4n+8)

Simplify the arithmetic:

-2n-14=-(4n+8)

Expand the parentheses:

2n14=4n8

Add to both sides:

(-2n-14)+4n=(-4n-8)+4n

Group like terms:

(-2n+4n)-14=(-4n-8)+4n

Simplify the arithmetic:

2n-14=(-4n-8)+4n

Group like terms:

2n-14=(-4n+4n)-8

Simplify the arithmetic:

2n14=8

Add to both sides:

(2n-14)+14=-8+14

Simplify the arithmetic:

2n=8+14

Simplify the arithmetic:

2n=6

Divide both sides by :

(2n)2=62

Simplify the fraction:

n=62

Find the greatest common factor of the numerator and denominator:

n=(3·2)(1·2)

Factor out and cancel the greatest common factor:

n=3

3. List the solutions

n=-113,3
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=2|n+7|
y=|4n+8|
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.