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Solution - Absolute value equations

Exact form: x=512,-124
x=\frac{5}{12} , -\frac{1}{24}
Decimal form: x=0.417,0.042
x=0.417 , -0.042

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
|3x-13|=|x+12|
without the absolute value bars:

|x|=|y||3x-13|=|x+12|
x=+y(3x-13)=(x+12)
x=-y(3x-13)=-(x+12)
+x=y(3x-13)=(x+12)
-x=y-(3x-13)=(x+12)

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||3x-13|=|x+12|
x=+y , +x=y(3x-13)=(x+12)
x=-y , -x=y(3x-13)=-(x+12)

2. Solve the two equations for x

18 additional steps

(3x+-13)=(x+12)

Subtract from both sides:

(3x+-13)-x=(x+12)-x

Group like terms:

(3x-x)+-13=(x+12)-x

Simplify the arithmetic:

2x+-13=(x+12)-x

Group like terms:

2x+-13=(x-x)+12

Simplify the arithmetic:

2x+-13=12

Add to both sides:

(2x+-13)+13=(12)+13

Combine the fractions:

2x+(-1+1)3=(12)+13

Combine the numerators:

2x+03=(12)+13

Reduce the zero numerator:

2x+0=(12)+13

Simplify the arithmetic:

2x=(12)+13

Find the lowest common denominator:

2x=(1·3)(2·3)+(1·2)(3·2)

Multiply the denominators:

2x=(1·3)6+(1·2)6

Multiply the numerators:

2x=36+26

Combine the fractions:

2x=(3+2)6

Combine the numerators:

2x=56

Divide both sides by :

(2x)2=(56)2

Simplify the fraction:

x=(56)2

Simplify the arithmetic:

x=5(6·2)

x=512

19 additional steps

(3x+-13)=-(x+12)

Expand the parentheses:

(3x+-13)=-x+-12

Add to both sides:

(3x+-13)+x=(-x+-12)+x

Group like terms:

(3x+x)+-13=(-x+-12)+x

Simplify the arithmetic:

4x+-13=(-x+-12)+x

Group like terms:

4x+-13=(-x+x)+-12

Simplify the arithmetic:

4x+-13=-12

Add to both sides:

(4x+-13)+13=(-12)+13

Combine the fractions:

4x+(-1+1)3=(-12)+13

Combine the numerators:

4x+03=(-12)+13

Reduce the zero numerator:

4x+0=(-12)+13

Simplify the arithmetic:

4x=(-12)+13

Find the lowest common denominator:

4x=(-1·3)(2·3)+(1·2)(3·2)

Multiply the denominators:

4x=(-1·3)6+(1·2)6

Multiply the numerators:

4x=-36+26

Combine the fractions:

4x=(-3+2)6

Combine the numerators:

4x=-16

Divide both sides by :

(4x)4=(-16)4

Simplify the fraction:

x=(-16)4

Simplify the arithmetic:

x=-1(6·4)

x=-124

3. List the solutions

x=512,-124
(2 solution(s))

4. Graph

Each line represents the function of one side of the equation:
y=|3x-13|
y=|x+12|
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.