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Solution - Absolute value equations

Exact form: x=-43,25
x=-\frac{4}{3} , \frac{2}{5}
Mixed number form: x=-113,25
x=-1\frac{1}{3} , \frac{2}{5}
Decimal form: x=1.333,0.4
x=-1.333 , 0.4

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
|x3|=|4x+1|
without the absolute value bars:

|x|=|y||x3|=|4x+1|
x=+y(x3)=(4x+1)
x=y(x3)=(4x+1)
+x=y(x3)=(4x+1)
x=y(x3)=(4x+1)

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||x3|=|4x+1|
x=+y , +x=y(x3)=(4x+1)
x=y , x=y(x3)=(4x+1)

2. Solve the two equations for x

11 additional steps

(x-3)=(4x+1)

Subtract from both sides:

(x-3)-4x=(4x+1)-4x

Group like terms:

(x-4x)-3=(4x+1)-4x

Simplify the arithmetic:

-3x-3=(4x+1)-4x

Group like terms:

-3x-3=(4x-4x)+1

Simplify the arithmetic:

3x3=1

Add to both sides:

(-3x-3)+3=1+3

Simplify the arithmetic:

3x=1+3

Simplify the arithmetic:

3x=4

Divide both sides by :

(-3x)-3=4-3

Cancel out the negatives:

3x3=4-3

Simplify the fraction:

x=4-3

Move the negative sign from the denominator to the numerator:

x=-43

10 additional steps

(x-3)=-(4x+1)

Expand the parentheses:

(x-3)=-4x-1

Add to both sides:

(x-3)+4x=(-4x-1)+4x

Group like terms:

(x+4x)-3=(-4x-1)+4x

Simplify the arithmetic:

5x-3=(-4x-1)+4x

Group like terms:

5x-3=(-4x+4x)-1

Simplify the arithmetic:

5x3=1

Add to both sides:

(5x-3)+3=-1+3

Simplify the arithmetic:

5x=1+3

Simplify the arithmetic:

5x=2

Divide both sides by :

(5x)5=25

Simplify the fraction:

x=25

3. List the solutions

x=-43,25
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|x3|
y=|4x+1|
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.