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Logarithms questions need checking

  1. Jul 30, 2009 #1
    1. ln (x2 / y2)
    = log (A / B) = logA-logB
    = logx2-logy2
    = 2logx - 2logy
    (is this correct)

    2. can this expression be split into seperate log functions and numbers, is this question the answer
    log(2x + 3y) = log(2x + 3y)
    (is this correct)
  2. jcsd
  3. Jul 30, 2009 #2
    What you have in 1. is correct, so you should be able to split, or expand, ln(x2/y2) correctly.
    For 2., where did log(2x + 3y) = log(2x + 3y) come from?
  4. Jul 30, 2009 #3


    Staff: Mentor

    For 1, you're mostly on the right track, but since you started with ln, you should end with ln. Also, you shouldn't have the business with A/B in there. IOW, it should look like this:
    ln (x2 / y2)
    = ln x2-ln y2
    = 2ln x - 2ln y

    You're pretty much done at this point, but this could also be written as 2(ln x - ln y), which is equal to 2 ln(x/y).

    For 2, there is nothing you can do with it. There is no property of logarithms that works on a sum of terms.
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