SOLUTION: log base x (w)=24, log base y (w)=40, log base xyz (w)=12. Find log base z (w).

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Question 1111152: log base x (w)=24, log base y (w)=40, log base xyz (w)=12. Find log base z (w).
Found 2 solutions by ikleyn, MathTherapy:
Answer by ikleyn(54060) About Me  (Show Source):
You can put this solution on YOUR website!
.
You are given

log%28x%2C%28w%29%29 = 24,      (1)

log%28y%2C%28w%29%29 = 40,      (2)

log%28xyz%2C%28w%29%29 = 12.    (3)



(1) is equivalent to   x%5E24 = w,          (1')

(2) is equivalent to   y%5E40 = w,          (2')

(3) is equivalent to   %28xyz%29%5E12 = w.       (3')


From (3')   %28xyz%29%5E120 = w%5E10,   or   x%5E120%2Ay%5E120%2Az%5E120 = w%5E10.    (4)


Replace here  x%5E120 by w%5E5  based on (1').   Replace  y%5E120  by w%5E3,  based on (2').  Then you will get


w%5E5%2Aw%5E3%2Az%5E120 = w%5E10,    which implies

z%5E120 = w%5E2  and then  z%5E60 = w.


The last equality means that  log%28z%2C%28w%29%29 = 60.


Answewr.  log%28z%2C%28w%29%29 = 60.

Solved.

--------------
On logarithms and their properties,  see the lessons
    - WHAT IS the logarithm
    - Properties of the logarithm
    - Change of Base Formula for logarithms
    - Solving logarithmic equations
    - Using logarithms to solve real world problems
in this site.

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 "Logarithms".


Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.



Answer by MathTherapy(10895) About Me  (Show Source):
You can put this solution on YOUR website!
log base x (w)=24, log base y (w)=40, log base xyz (w)=12. Find log base z (w).

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                          w+=+%28xyz%29%5E12. Substituting matrix%282%2C1%2C+%22+%22%2C+w%5E%281%2F24%29%29 for x, and matrix%282%2C1%2C+%22+%22%2C+w%5E%281%2F40%29%29 for y, we get:
      
            ----- Dividing each side by matrix%282%2C1%2C+%22+%22%2C+w%5E%288%2F10%29%29
           
                w%2Fmatrix%282%2C1%2C+%22+%22%2C+w%5E%288%2F10%29%29+=+z%5E12%29
          matrix%282%2C1%2C+%22+%22%2C+w%5E%281+-+8%2F10%29+=+z%5E12%29  
               matrix%282%2C1%2C+%22+%22%2C+w%5E%282%2F10%29+=+z%5E12%29
                 matrix%282%2C1%2C+%22+%22%2C+w%5E%281%2F5%29+=+z%5E12%29
         matrix%282%2C1%2C+%22+%22%2C+w%5E%28%281%2F5%295%29+=+z%5E%2812+%2A+5%29%29 --- Raising each side to the 5th power 
                       w+=+z%5E60 
             highlight%28log+%28z%2C+%28w%29%29+=+60%29 ------- Converting to LOGARITHMIC form