Using a Rule of LogarithmsDate: 9/13/95 at 22:12:37 From: Anonymous Subject: Math problem--I need help I am a 9th grader and taking Algebra II. I can't figure out this problem. Can you help? log(sub)2 3k+log(sub)2 5=log(sub)2 45. Thanks, doc. Joey Jackson Date: 9/14/95 at 9:34:9 From: Doctor Ethan Subject: Re: Math problem--I need help Well, here is what you do. First you need to realize a rule about logs. Assuming they have the same base, this is always true. Log a + Log b = Log a * b So we can take your problem (I am going to leave off the base two stuff) and we have Log 3k + log 5 = log 45 but by our formula we have log (3k) (5) = log 45 This is Log 15k = log 45 But if the log of 15k equals the log of 45 then 15k must equal 45 So we have 15k = 45 so k = 3. Does this make sense? I hope this works for you. - Doctor Ethan, The Geometry Forum |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2015 The Math Forum
http://mathforum.org/dr.math/