Problem with a logarithmic rule

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Discussion Overview

The discussion revolves around the rules of logarithms, specifically focusing on the manipulation of logarithmic expressions involving inversion of numbers and sign changes. Participants explore the implications of these manipulations in the context of logarithmic identities and equations.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant seeks clarification on why inverting numbers in logarithmic expressions and changing the sign yields the same result.
  • Another participant states the logarithmic identity ln(a^b) = b*ln(a) and suggests testing it with b = -1.
  • A participant presents the identity ln(A/B) = ln(A) - ln(B) and demonstrates how it can be rewritten as -ln(B/A).
  • Further, a participant elaborates on an equation involving logarithms, showing that multiplying the numerator and denominator by -1 leads to a transformation of the logarithmic expression, ultimately flipping the argument inside the logarithm.
  • A final participant expresses gratitude for the contributions made in the discussion.

Areas of Agreement / Disagreement

The discussion does not reach a consensus, as participants present various manipulations and identities without resolving the initial query about the inversion and sign change in logarithmic rules.

Contextual Notes

Some assumptions about the properties of logarithms are implicit, and the discussion does not clarify all mathematical steps involved in the transformations presented.

mrcotton
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Please could some one help me with the rules of logarithms to understand why inverting the numbers in the bracket and change the minus sign to a plus sign gives the same result?

Thank you
 
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ln(a^b)=b*ln(a)
Try b=-1
 
ln(A/B) = ln(A) - ln(B) = -[ln(B) - ln(A)] = -ln(B/A)
 
for the equation on the right: t= ( ln (N0/N) ) / λ:

if you multiply top and bottom of the fraction by -1 you get

t= (-1 ln (N0/N)) / -λ

You have -1 ln (N0/N) which is equal to ln( (N0/N)^-1 ) by the power rule. The (N0/N)^-1 inside the log flips to (N/N0) from the negative exponent and you get:

t= ( ln (N/N0) ) / -λ.
 
Fantastic thanks to you all
 

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