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Solution - Absolute value equations

Exact form: x=72
x=\frac{7}{2}
Mixed number form: x=312
x=3\frac{1}{2}
Decimal form: x=3.5
x=3.5

Other Ways to Solve

Absolute value equations

Step-by-step explanation

1. Rewrite the equation with one absolute value terms on each side

|x+3|+|x+4|=0

Add |x+4| to both sides of the equation:

|x+3|+|x+4||x+4|=|x+4|

Simplify the arithmetic

|x+3|=|x+4|

2. 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
|x+3|=|x+4|
without the absolute value bars:

|x|=|y||x+3|=|x+4|
x=+y(x+3)=(x+4)
x=y(x+3)=(x+4)
+x=y(x+3)=(x+4)
x=y(x+3)=(x+4)

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||x+3|=|x+4|
x=+y , +x=y(x+3)=(x+4)
x=y , x=y(x+3)=(x+4)

3. Solve the two equations for x

12 additional steps

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

Expand the parentheses:

(-x+3)=x-4

Subtract from both sides:

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

Group like terms:

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

Simplify the arithmetic:

-2x+3=(x-4)-x

Group like terms:

-2x+3=(x-x)-4

Simplify the arithmetic:

2x+3=4

Subtract from both sides:

(-2x+3)-3=-4-3

Simplify the arithmetic:

2x=43

Simplify the arithmetic:

2x=7

Divide both sides by :

(-2x)-2=-7-2

Cancel out the negatives:

2x2=-7-2

Simplify the fraction:

x=-7-2

Cancel out the negatives:

x=72

6 additional steps

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

NT_MSLUS_MAINSTEP_RESOLVE_DOUBLE_MINUS:

(-x+3)=-x+4

Add to both sides:

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

Group like terms:

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

Simplify the arithmetic:

3=(-x+4)+x

Group like terms:

3=(-x+x)+4

Simplify the arithmetic:

3=4

The statement is false:

3=4

The equation is false so it has no solution.

4. List the solutions

x=72
(1 solution(s))

5. Graph

Each line represents the function of one side of the equation:
y=|x+3|
y=|x+4|
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.