IB MATH TYPE I Portfolio - LOGARITHM BASES

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LOGARITHM BASES

Purpose: My purpose for this investigation was to find the general statement that expresses logabx, in the terms of c and d. I was able to achieve this goal through the process of finding the expression for the nth term in various different sequences.

In the beginning stages of my investigation I came across the sequence of

        Log28, Log48, Log88, Log168, Log328.......

While I was looking at this sequence I came to the realization that the base of the log form was increasing at a constant pattern. I realized that the base of 2 was being raised to the power of the term number. Therefore the second term has a base of 4 due to the fact that 2 raised to the power of 2(term number) equals 4. Even though the base changes the 8 stays constant and this also means that I would be able to continue the pattern.

        6th term = log(2˄6)8                                  7th term = log(2˄7)8

                      = log648                                                    = log1288

After continuing the pattern I realized the next step would be to solve this problem and discover what exponent we need to raise to base to, in order to achieve the answer of 8. So I decided to change my pattern from log form into exponential form.

        2x=8,    4x=8,    8x=8,    16x=8,    32x=8,    64x=8,    128x=8

After successfully converting into exponential form I decided to take this a step further and make all the bases the same throughout the sequence.

        2x=23,        22x=23,      23x=23,      24x=23,      25x=23,     26x=23,      27x=23

Once I had converted all the bases to be the same I came to see another pattern that was set-up within the sequence and that was that..

                                2nx = 23

In this equation n is equal to the nth number. However this equation could be simplified even further due to the fact that the bases are equivalent.

                                 nx=3

                                x=3/n 

Through this equation you are able to determine the x value through dividing 3 by the nth value. By discovering the x value I am able to determine what exponent I need to the base to in order to achieve a value of 8 in said sequences.

   Now that I have concluded an expression I will test its validity for log281, log481, log881:

        x=3/n             x=3/n                 x=3/n

        x=3/1             x=3/2                 x=3/3

        x=3                 x=1.5                  x=1

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Now I will check my answer:

             =Log28                        =Log48                      =Log88

        

=Log8                           =Log8                       =Log8

           Log2                       Log4                  Log8

        

           =3                     =1.5                    =1     

           23=8                     41.5=8         ...

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