Changing the base of a logarithm

In summary, the conversation discusses how to express \log_4(12) in terms of p, given that \log_8(6) = p. It is suggested to express everything in terms of \log_2 and use the Change of Base Formula. One possible solution is found to be \log_4(12) = (1/p)(\log_4(2) + \log_4(6)). The conversation also includes hints and reminders for solving the problem.
  • #1
Jouster
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Homework Statement
I'm unsure of how to solve this problem, I tried changing the bases but they don't seem to have any similarities
Relevant Equations
Expressing values in terms of another
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  • #2
Jouster said:
Homework Statement:: I'm unsure of how to solve this problem, I tried changing the bases but they don't seem to have any similarities

Given [itex]\log_8(6) = p[/itex], express [itex]\log_4(12)[/itex] in terms of [itex]p[/itex].

Given that [itex]8 = 2^3[/itex] and [itex]4 = 2^2[/itex], expressing everything in terms of [itex]\log_2[/itex] seems like a good idea.
 
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  • #3
The equation ##\log_8(6) = p## can be rewritten as ##6 = 8^p##. It's not too difficult to get from there to an equation involving ##\log_4(12)## that involves p.
 
  • #4
pasmith said:
Given that [itex]8 = 2^3[/itex] and [itex]4 = 2^2[/itex], expressing everything in terms of [itex]\log_2[/itex] seems like a good idea.
I did express everything in terms of log2, I got
log8(6) = log26/log28 = p
log4(12) = log212/log24
But I don't understand how to use this information & solve the problem :biggrin:
 
  • #5
The Change Of Base Formula, as learned in Intermediate Algebra course?
 
  • #6
I tried but without using Change Of Base formula.
One step I found p*log_4(8)=log_4(6)
(Excuse the lack of great typesetting.)
and notice that 12=1.5*8, and 12=2*6; and continued on that way.

Lastly I found log_4(12)=(1/p)(log_4(2)+log_4(6).
Not sure if that is what was wanted. Also not absolutely sure it is correct - not feel like checking carefully.
 
  • #7
Jouster said:
But I don't understand how to use this information & solve the problem :biggrin:
Some useful hints: ##\log_{2}4=\log_{2}2^{2}##, ##\log_{2}8=\log_{2}2^{3}##, ##\log_{2}6=\log_{2}\left(2\times3\right)##, ##\log_{2}12=\log_{2}\left(2^{2}\times3\right)##.
 
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  • #8
Jouster said:
I did express everything in terms of log2, I got
log8(6) = log26/log28 = p
log4(12) = log212/log24
But I don't understand how to use this information & solve the problem :biggrin:

But you didn't notice that [itex]\log_2 8 =\log_2(2^3) =3[/itex] and [itex]\log_2(4) = 2[/itex], or that [itex]\log_2(12) = \log_2(2 \times 6) = 1 + \log_2(6)[/itex]?
 
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FAQ: Changing the base of a logarithm

What is the purpose of changing the base of a logarithm?

The purpose of changing the base of a logarithm is to simplify complex logarithmic expressions and make them easier to solve. It also allows for easier comparison between different logarithms.

How do you change the base of a logarithm?

To change the base of a logarithm, you can use the change of base formula: logb(x) = loga(x) / loga(b), where b is the desired base and a is the current base. This formula can be used for both natural logarithms (base e) and common logarithms (base 10).

What is the difference between natural logarithms and common logarithms?

Natural logarithms have a base of e (approximately 2.718), while common logarithms have a base of 10. This means that natural logarithms are used more frequently in mathematical and scientific calculations, while common logarithms are commonly used in practical applications such as measuring pH levels and earthquake magnitudes.

Can you change the base of any logarithm?

Yes, you can change the base of any logarithm using the change of base formula. However, it is important to note that some bases may result in irrational or complex numbers, which may not be practical or useful in certain situations.

What are some real-life applications of changing the base of a logarithm?

Changing the base of a logarithm is commonly used in finance to calculate compound interest and in chemistry to calculate pH levels. It is also used in computer science and data analytics to measure the complexity of algorithms and data structures.

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