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Solution - Absolute value equations

Exact form: a=3,3
a=3 , -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
|a6|=|2a+3|
without the absolute value bars:

|x|=|y||a6|=|2a+3|
x=+y(a6)=(2a+3)
x=y(a6)=(2a+3)
+x=y(a6)=(2a+3)
x=y(a6)=(2a+3)

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||a6|=|2a+3|
x=+y , +x=y(a6)=(2a+3)
x=y , x=y(a6)=(2a+3)

2. Solve the two equations for a

11 additional steps

(a-6)=(-2a+3)

Add to both sides:

(a-6)+2a=(-2a+3)+2a

Group like terms:

(a+2a)-6=(-2a+3)+2a

Simplify the arithmetic:

3a-6=(-2a+3)+2a

Group like terms:

3a-6=(-2a+2a)+3

Simplify the arithmetic:

3a6=3

Add to both sides:

(3a-6)+6=3+6

Simplify the arithmetic:

3a=3+6

Simplify the arithmetic:

3a=9

Divide both sides by :

(3a)3=93

Simplify the fraction:

a=93

Find the greatest common factor of the numerator and denominator:

a=(3·3)(1·3)

Factor out and cancel the greatest common factor:

a=3

11 additional steps

(a-6)=-(-2a+3)

Expand the parentheses:

(a-6)=2a-3

Subtract from both sides:

(a-6)-2a=(2a-3)-2a

Group like terms:

(a-2a)-6=(2a-3)-2a

Simplify the arithmetic:

-a-6=(2a-3)-2a

Group like terms:

-a-6=(2a-2a)-3

Simplify the arithmetic:

a6=3

Add to both sides:

(-a-6)+6=-3+6

Simplify the arithmetic:

a=3+6

Simplify the arithmetic:

a=3

Multiply both sides by :

-a·-1=3·-1

Remove the one(s):

a=3·-1

Simplify the arithmetic:

a=3

3. List the solutions

a=3,3
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|a6|
y=|2a+3|
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.