SOLUTION: Hi, I have the question 5n + 24 = |8 - 3n| for my homework and I've gotten -2 and -16 as the answers, but I don't know if that's correct or if it would only be -2 as the answer

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Question 1091097: Hi, I have the question 5n + 24 = |8 - 3n| for my homework and I've gotten -2 and -16 as the answers, but I don't know if that's correct or if it would only be -2 as the answer
Answer by ikleyn(52847)   (Show Source): You can put this solution on YOUR website!
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5n + 24 = |8 - 3n|
~~~~~~~~~~~~~~~

1.  First of all, you can easily check if your numbers satisfy the equation.

    For n = -2 you have

    a)  left side is  5*(-2) + 24 = -10 + 24 = 14.
    b)  right side is  |8 - 3*(*(-2)| = |8 + 6| = 14.

    So, n = -2 is the solution.



    For n = -16 you have 

    a)  left side is  5*(-16) + 24 = -80 + 24 = -56.
    b)  right side is  |8 - 3*(-16)| = |8 + 48| = 56.

    So, n = 16 is not the solution.



2.  The plots of the functions are shown below:


    


Plots y = 5x + 24 (red) and  y = |8 - 3x| (green)

These plots (graphical solution) show you visually that there is only one solution.

Surely, from the mathematical point of view, it is not the proof.
It is only visual evidence.

3.  Now I will show you how to solve this equation

    5n + 24 = |8 - 3n|.     (1)


    Looking into the right sde, you can notice that there is the critical point n =  =  .


     Case a)  If  n <= ,  then 8 - 3n >= 0, and the right side of the equation (1) is 8-3n.

              Hence, in this case the equation (1) takes the form

              5n + 24 = 8 - 3n.    (2)

              Simplify it further and solve for n:

              5n + 3n = 8 - 24  ====>  8n = -16  ====>  n = -2.

              This value of n satisfy the inequality  n <= .
              Hence,  n = -2  is the solution to (2)  and  is the solution to (1).

              Case a)  is completed.



     Case b)  If  n > ,  then 8 - 3n < 0, and the right side of the equation (1) is 3n-8.

              Hence, in this case the equation (1) takes the form

              5n + 24 = 3n - 8.    (3)

              Simplify it further and solve for n:

              5n - 3n = -8 - 24  ====>  2n = -32  ====>  n = -16.

              But this value of n DOES NOT satisfy the inequality  n > .
              Hence,  n = -16, alghough  is the solution to (3),  IS NOT the solution to (1).

              Case b)  is completed.

Thus we found that the only solution to the given equation  (1)  is   n= -2.


        **************
        *** Solved ***
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To see more similar solved problems/  (your samples),  look into the lessons
    - Absolute Value equations
    - HOW TO solve equations containing Linear Terms under the Absolute Value sign. Lesson 1
    - HOW TO solve equations containing Linear Terms under the Absolute Value sign. Lesson 2
    - HOW TO solve equations containing Linear Terms under the Absolute Value sign. Lesson 3

    - HOW TO solve equations containing Quadratic Terms under the Absolute Value sign. Lesson 1
    - HOW TO solve equations containing Quadratic Terms under the Absolute Value sign. Lesson 2
    - OVERVIEW of lessons on Absolute Value equations
in this site.

Read them attentively and become an expert in this area.


Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic
"Solving Absolute values equations".



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