Is log8 (x/2) same as log8 x/2?

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Discussion Overview

The discussion revolves around the interpretation of the logarithmic expressions log8 (x/2) and log8 x/2. Participants explore the implications of notation and the importance of parentheses in mathematical expressions, particularly in the context of logarithms.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants question whether log8 (x/2) is equivalent to log8 x/2, highlighting the ambiguity in notation.
  • One participant suggests that the interpretation of the expressions can vary based on hidden assumptions in the notation, listing several possible interpretations.
  • Another participant emphasizes the importance of using parentheses to clarify expressions, noting that the order of operations for logarithms is not as straightforward as for other mathematical operations.
  • A participant reflects on their past experience with similar questions in high school, indicating that even educators may struggle with these concepts.
  • Some participants propose that without parentheses, log8 x/2 could be interpreted as (log8 x)/2, which differs from log8 (x/2).
  • One participant advocates for the consistent use of parentheses to avoid confusion and suggests substituting values for x to test the expressions.

Areas of Agreement / Disagreement

Participants generally agree on the need for clarity in notation and the use of parentheses, but there is no consensus on the equivalence of the two logarithmic expressions. Multiple interpretations remain contested.

Contextual Notes

The discussion highlights the potential for misinterpretation due to ambiguous notation and the varying conventions in mathematical expressions, particularly in logarithmic contexts.

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Is log8 (x/2) same with log8 x/2?
 
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wzwz said:
Is log8 (x/2) same with log8 x/2?
Can you compute them and find out?
 
Depends on what is hidden behind this sloppy notation:
$$
\log (8 \cdot \dfrac{x}{2})\; , \; \log \dfrac{8x}{2} \; , \; \dfrac{x}{2} \cdot \log 8 \; , \; \log_8 \dfrac{x}{2} \; , \; \dfrac{1}{2}\cdot \log_8 x \; , \;\dfrac{1}{2}\cdot \log (8x) \; , \;\dfrac{1}{2}\cdot x \cdot \log 8
$$
Make your choice.
 
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The order of operations is well defined for exponents, and multiplication, and addition, but how it works with the log function doesn't seem to be nearly so conventional. When in doubt, use parentheses. When I was a high school student studying algebra in 1972, I asked the teacher the same question, about the order of operations for the log function. He didn't know the answer, and/or didn't understand the question.
 
wzwz said:
Is log8 (x/2) same with log8 x/2?
To elaborate on what @fresh_42 said, what you wrote isn't clear. The second expression might be interpreted as ##\frac{\log_8 x}{2}##, which is different from ##\log_8 \frac x 2##.
 
Without parenthesis, I would read log8 x/2 as (log8 x)/2. Parenthesis are cheap. Use them.
 
wzwz said:
Is log8 (x/2) same with log8 x/2?

First of all, use parentheses, everywhere. Even when they are redundant. Make it absolutely clear that no errors can be made if you follow the parentheses. Usually it doesn't matter much, but in this question, it is impossible to distinguish the bases from the actual values without proper parentheses and terms.

Instead of the forum helping you, just set x equal to anything and do what you think it is.

If you ever have to check a property in math, just set the variable equal to 1, and solve. It can be in logarithms, exponents, etc. Just make everything into simple numbers that can be calculated and check.
 

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