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Solution - Absolute value equations

Exact form: b=7,7
b=7 , -7

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
|b7|=|b+7|
without the absolute value bars:

|x|=|y||b7|=|b+7|
x=+y(b7)=(b+7)
x=y(b7)=(b+7)
+x=y(b7)=(b+7)
x=y(b7)=(b+7)

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||b7|=|b+7|
x=+y , +x=y(b7)=(b+7)
x=y , x=y(b7)=(b+7)

2. Solve the two equations for b

11 additional steps

(b-7)=(-b+7)

Add to both sides:

(b-7)+b=(-b+7)+b

Group like terms:

(b+b)-7=(-b+7)+b

Simplify the arithmetic:

2b-7=(-b+7)+b

Group like terms:

2b-7=(-b+b)+7

Simplify the arithmetic:

2b-7=7

Add to both sides:

(2b-7)+7=7+7

Simplify the arithmetic:

2b=7+7

Simplify the arithmetic:

2b=14

Divide both sides by :

(2b)2=142

Simplify the fraction:

b=142

Find the greatest common factor of the numerator and denominator:

b=(7·2)(1·2)

Factor out and cancel the greatest common factor:

b=7

5 additional steps

(b-7)=-(-b+7)

Expand the parentheses:

(b-7)=b-7

Subtract from both sides:

(b-7)-b=(b-7)-b

Group like terms:

(b-b)-7=(b-7)-b

Simplify the arithmetic:

-7=(b-7)-b

Group like terms:

-7=(b-b)-7

Simplify the arithmetic:

7=7

3. List the solutions

b=7,7
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|b7|
y=|b+7|
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.