How do you solve abs(3-x)-1=abs(4x+2)?

1 Answer
Jul 17, 2015

color(red)(x = 0)

Explanation:

We have two absolute conditions, so we must write four different equations without the absolute value symbols and solve for x.

Your original equation is

|3-x|-1 = |4x+2|

So these equations would be

(1): ** (3-x) -1 = (4x+2)
(2): ** (3-x) - 1 = -(4x+2)
(3): ** -(3-x) - 1 = (4x+2)
(4): ** -(3-x) - 1 = -(4x+2)

Solve Equation 1:

(3-x) -1 = (4x+2)
3-x-1 = 4x+2
2-x = 4x+2
-x = 4x
0 = 5x
x = 0

This is a possible solution, which we will check later.

Solve Equation 2.

(3-x) -1 = -(4x+2)
3-x-1 = -4x-2
2-x = -4x-2
-x = -4x
0 = -3x
x = 0

This is a possible solution, which we will check later.

Solve Equation 3.

-(3-x) - 1 = (4x+2)
-3+x-1 = 4x+2
x-4 = 4x+2
3x = -6
x = -2

This is a possible solution, which we will check later.

Solve Equation 4.

-(3-x) - 1 = -(4x+2)
-3+x-1 = -4x-2
x-4 = -4x-2
5x = 2
x = 2/5

This is a possible solution, which we will check later.

Check Solutions 1 and 2

If x=0

|3-x|-1 = |4x+2|
|3-0|-1 = |4×0+2|
|3|-1 =|0+2|
3-1= |2|
2 = 2

Check Solution 3

If x = -2

|3-x|-1 = |4x+2|
|3-(-2)|-1 = |4(-2)+2|
|3+2| -1 = |-8 +2|
|5| -1 = |-6|
5-1 = 6
4 = 6

This is an impossible result. x = -2 is not a solution.

Check Solution 4

If x = 2/5

|3-x|-1 = |4x+2|
|3-2/5|-1 = |4×2/5+2|
|15/5-2/5|-1 = |8/5+10/5|
|13/5|-1 = |18/5|
13/5 – 1 = 18/5
13/5- 5/5 = 18/5
8/5 = 18/5

This is an impossible result. x = 2/5 is not a solution.

The only solution is x = 0.