Another log problem! Help plz?

Posted by admin
physics ques asked:


How do you show

log(base 3)3^(2x) = log(base 3) 4

I’m assuming you look at each side separately but not completely sure if someone could show me that would be great thanks

Vincent

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  • 2 Responses to “Another log problem! Help plz?”

    1. Steven X Says:

      The left hand side involves x, whereas the right hand side does not. Hence, this is not an identity that you prove (”show”), but rather an equation that is to be solved.

      Raise both sides to the power of 3 to cancel the log(base3) on both sides.

      We have 3^(2x) = 4.

      Taking natural logarithms of both sides and dividing over, we have
      2x = ln4/ln3
      x = ln4/2ln3

    2. Carl L Says:

      log(base 3)3^(2x) = log(base 3) 4

      Using the properties of logarithms, pull out the exponents

      (2x)(log(base 3)3) = log(base 3) 4

      log(base 3) of 3 is 1, so

      2x = log(base 3) 4

      x = 1/2*log(base 3) 4 = log(base 3) 4^(1/2) = log(base 3) 2