Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How do I evaluate this log expression?

  1. Jan 4, 2010 #1
    1. The problem statement, all variables and given/known data
    5^(log510-1)
    2. Relevant equations
    n/a
    3. The attempt at a solution
    I have no idea how to approach this.
     
  2. jcsd
  3. Jan 4, 2010 #2

    CompuChip

    User Avatar
    Science Advisor
    Homework Helper

    Well, you know what

    [tex]5^{\log_5(x)}[/tex]
    is, don't you?

    Then there are two ways to solve the question: you can split the sum in the power to a multiplication:
    [tex]5^{a + b} = 5^a \cdot 5^b[/tex]

    or you can first write 1 as a logarithm (base 5), then combine the two logarithms into one.
     
  4. Jan 5, 2010 #3
    Do you know that exponentials and logarithms are inverses of each other?
    y = ax [itex]\Longrightarrow[/itex] x = logay
    Then, after substituting the x, [tex] y = a^{\log_a y}[/tex]
    So what is [tex]5^{\log_5 x}[/tex] ?

    Perhaps you should review http://en.wikipedia.org/wiki/Logarithm" [Broken].
     
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook